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CBSE Grade 12 Chemistry Extra Practice Questions
CBSE Class 12 Chemistry 2023 practice questions will help students to score well on CBSE 2023 exam. /. Students taking the CBSE 2023 exam must pass all CBSE Class 12 2023 Chemistry Practice Questions provided on this page and bookmark this page for the latest updates from the Central Board of Secondary Education.
CBSE Grade 12 Chemistry Extra Practice Questions
To achieve the highest grade in Grade 12 Chemistry, candidates are required to practice the CBSE 2023 Grade 12 Chemistry practice questions provided on this page and consolidate all formulas, chemical reactions and chemistry concepts provided in the syllabus of CBSE. Students are required to complete the CBSE 2023 Class 12 Chemistry Practice Questions to assess their chemistry readiness for the CBSE 2023 exam.
Grade 12 Chemistry CBSE 2023 Extra Practice Questions: Exam Pattern
Here we provide the sample chemistry exam according to the paper model published by the board on its official website. The CBSE Chemistry Quiz is divided into three sections namely Section A, Section B and Section C. Please review the additional information given below:
Section A:This section asks very short 2 point answer questions.
Section b:This section asks short answer questions, each worth 3 points.
Section C:In this section, questions related to the case are asked for 5 points each.
2023 Grade 12 Chemistry Additional Practice Questions: General Notes
Subject: CHEMISTRY (043)
Maximum notes: 70
Allowed time: 3 hours
General instructions:
Please read the following instructions carefully.
a) There are 35 questions in this internally selected question booklet.
b) SECTION A consists of 18 multiple choice questions of 1 point each.
c) SECTION B consists of 7 very short answer questions of 2 points each.
d) SECTION C consists of 5 short-answer questions of 3 points each.
e) BLOCK D consists of 2 long-answer questions of 4 points each.
f) SECTION E consists of 3 long-answer questions of 5 points each.
g) All questions are mandatory.
h) The use of registration tables and pocket calculators is not allowed.
Chemistry Class 12 of 2023 Bonus Practice Questions:SECTION A
The following questions are multiple choice questions with one correct answer. Each question is worth 1 point. There is no built-in selection in this section.
P.1 De-icing is the removal of snow, ice, or frost from a surface. In extremely cold regions, car windows are covered in ice, reducing visibility. The image below shows a car window being defrosted with a liquid in extremely cold conditions. Which of the following compounds could be present in the deicing fluid used above?
A. formaldehyde
B. Fenol
C. Propan-2-ol
D. Acetic acid
Q.2 Which of the following reaction mechanisms is not involved in the given reaction sequence?
A. Replacement of free radicals
B. nucleophilic substitution
C. Elimination
D. Nucleophilic addition-elimination
Q.3 The graph below shows the observed standard electrode potential of some transition elements. Which of the following reactions can be predicted from the graph above?
A. Cu + 2 H2SO4 -> CuSO4 + SO2 + 2 H2O
B. Cu + 2 HNO3 → Cu(NO3)2 + H2
C. CuO + 2 HCl –> CuCl2 + H2O
D. Cu2+ + 2 NaOH –> Cu(OH)2 + 2 Na+
Q.4 Kamlesh conducted an experiment to find the rate equation for the following reaction:
2NO+O2 -> 2NO2
He measured the rate of this reaction as a function of the initial concentrations of the reactants as follows:
Which of the following could be a reason for the inconsistency of the initial NO2 formation rate for Experiment 4?
A. The rate of reaction does not depend on the concentration of the reactants.
B. A higher O2 concentration may have resulted in a decreased rate of reaction.
C. A higher concentration of NO may have caused a reduction in the reaction rate.
D. The temperature of the reagents in Experiment 4 may have differed from the other experiments.
Q.5 The following image shows the electrolysis of an electrolyte using a DC voltage source. Based on this, which of the following statements is (are) correct?
(i) The solution remains electrically neutral during electrolysis.
(ii) Electrons flow from the power source into solution at one electrode and an equal number of electrons flow out of solution at the other electrode.
(iii) The number of positive ions moving towards one electrode is always equal to the number of negative ions moving towards the other electrode.
A. I only
B. solo i y ii
C. ii and iii only
D. todo-i, ii e iii
Q.6 For a given reaction X, rate = 0.7ZABe-EA/RT. It can be seen that for another reaction Y, Rate = ZABe-EA/RT.
Based on the above, what can be said about reactions X and Y?
A. Both reactions involve complex molecules.
B. Both reactions involve individual molecules or atomic species.
C. Reaction X involves simple molecules or atomic species, while reaction Y involves complex molecules.
D. Reaction X involves complex molecules, while reaction Y involves simple molecules or atomic species.
Q.7 A metal ion Mn+ forms a complex ion of the formula [ML2](n-4)+ where L represents a bidentate ligand. Which of the following could be the charge of ligand L?
A.-2
B-1
C 0
D +2
F.8 The image below shows various derivatives of benzene that give mononitration products in the ortho, meta, and para positions together with the ratio of nitration to benzene. Which of the following lines shows at least one INCORRECT description of the reaction?
A. only B
B solo C
C solo B y C
D solo C y D
Q.9 The rate constants of a reaction at 400 K and 600 K are 5 x 10-3s–1y 8x10-3s–1And what additional information is needed to calculate the value of A (frequency factor)? (According to the Arrhenius equation, the rate constant is given by k = Ae-Ea/RT.)
A. The order of the reaction.
B. the activation energy of the reaction
C. The initial concentration of the reactants.
D. [No additional information is required. A can be calculated from the available information]
Q.10 The compound [Co(NH3)5Cl]SO4 is an isomer of the compound [Co(NH3)5SO4]Cl. Which of the following lines correctly represents the oxidation state of cobalt in these compounds? Rows [Co(NH3)5Cl]SO4 [Co(NH3)5SO4]Cl
And +2 +3
B +3 +2
C +2 +1
D +3 +3
AA
BED AND BREAKFAST
CC
D.D.
Q.11 The following image shows an experimental setup for the production of an organic product X. Which of the following could be "X"?
A.Ethan
B. eteno
c. acetic acid
D. Diethyl ether
F.12 During protein synthesis in cells, amino acids are condensed (in the presence of enzymes) through the formation of amide bonds (–CONH–) or peptide bonds to form a polypeptide chain, which then folds into a biologically responsible active protein. The following equation shows the formation of a dipeptide, Ala-Gly, formed by the condensation of two amino acids, alanine and glycine, in a test tube. Which of the following statements is true of the above reaction?
(i) It is also likely that a Gly-Ala dipeptide is formed by the condensation of alanine and glycine.
(ii) Water is removed in the above condensation reaction.
(iii) Oxygen and hydrogen are given off as gases in the above condensation reaction.
A. I only
B. solo i y ii
C. ii and iii only
D. todo-i, ii e iii
Q.13 Zirconium (Zr, atomic number 40) and hafnium (Hf, atomic number 72) are Group 4 transition series metals. They occur together in nature and are difficult to separate. Which of the following is the reason for the above?
A. The nearly identical radii of the atoms.
B. The elements belong to the same group.
C. The elements belong to adjacent periods.
D. The presence of the same number of unpaired electrons in both elements.
Q.14 Which of the following would be among the reaction products between the reactions of ammonia with bromoethane?
(e) CH3CH2N.H2
(ii) (CH3CH2)2N.H
(iii) (CH3CH2)3norte
(iv) (CH3CH2)4norte+brother−
a. just me
B. solo i y ii
C. i, ii and iii only
D. all-i, ii, iii y iv
1
Q.15 Below are two statements labeled Statement (A) and Reason (R).
Statement (A): Dimethylamine has a higher boiling point than trimethylamine.
Reason (R): The molecular weight of trimethylamine is relatively higher than that of dimethylamine.
Select the most appropriate answer from the following options:
A. Both A and R are true, and R is the correct statement of A.
B. Both A and R are true, but R is not the correct explanation of A.
C. A is true but R is false.
D. A is false but R is true.
Q.16 Below are two statements labeled Statement (A) and Reason (R).
Statement (A): A silver mirror can be created with ethanal on the side of a test tube.
Reason (R): Ethanal can react with Fehling's solution
Select the most appropriate answer from the following options:
A. Both A and R are true, and R is the correct statement of A.
B. Both A and R are true, but R is not the correct explanation of A.
C. A is true but R is false.
D. A is false but R is true.
Q.17 Below are two statements called Statement (A) and Reason (R).
Statement (A): At constant temperature, the dissociation constant of chloroethanoic acid is greater than that of propionic acid.
Ratio (R): The more carbon atoms in a compound, the lower the dissociation constant.
Select the most appropriate answer from the following options:
A. Both A and R are true, and R is the correct statement of A.
B. Both A and R are true, but R is not the correct explanation of A.
C. A is true but R is false.
D. A is false but R is true.
Q.18 Below are two statements labeled Statement (A) and Reason (R).
Statement (A): At room temperature, propan-2-ol and 2-methylpropan-2-ol, when heated with acidified potassium dichromate, slowly change color from orange dichromate to green.
Ratio (R): Secondary and tertiary alcohols are easily oxidized to aldehydes, which are oxidized to acids.
Select the most appropriate answer from the following options:
A. Both A and R are true, and R is the correct statement of A.
B. Both A and R are true, but R is not the correct explanation of A.
C. A is true but R is false.
D. Both A and R are wrong.
Chemistry Class 12 of 2023 Bonus Practice Questions:SECTION B
This section contains 7 questions with an internal choice of two questions. The following questions are very short response types and are worth 2 points each.
Q.19 At high temperatures, ethyl chloride produces HCl and ethylene by the following first-order reaction:
CH3CH2Cl -> HCl + C2H4
In an experiment with an initial concentration of ethyl chloride of 0.01 M, the reaction rate was 1.6 x 10-8IN. What is the reaction rate when the initial concentration of ethyl chloride is 0.07 M?
F.20 Pineapples contain a protease enzyme that breaks down protein. if you try one
Jam made with fresh pineapple chunks, the jam will not curdle, but it will if you use canned food
Pineapple. To explain.
O
The structure of the lysine chain is shown below.
(i) Based on structure, is lysine acidic, basic, or generally neutral? To explain.
(ii) What is the structure of lysine when placed in a pH 1 solution?
Q.21 2-bromooctane reacts with alcoholic NaOH to form 2-octanol as shown below.
(a) Identify the nature of the substitution reaction mechanism. Justify your answer.
(b) What is the effect on the reaction rate when:
(i) is the NaOH concentration halved?
(ii) is the concentration of 2-bromooctane halved?
O
(a) Which of the following two compounds has a chiral center?
(b) Two compounds X and Y are enantiomers of each other.
Name a physical property that:
(i) is the same for X and Y.
(ii) is different for X and Y.
Q.22 (i) The complex [PtCl2(NH3)2] has two isomers, while [CoCl4]2-does not exhibit geometric isomerism and has no isomers, why?
(ii) When a solution of NaOH is added to an aqueous solution of copper(II) sulfate, the hydroxide ions displace the water molecules to form a light blue precipitate, X. When an excess of ammonia is added, the molecules of water and hydroxide ions are exchanged for ammonia molecules. , Formation of a dark blue solution, Y. Identify X and Y.
Q.23 A semi-equation for a redox reaction represents an equilibrium between two sides of an equation such as:
copper2+(aq) + 2e- —> Cu (s); Eo= +0,34v
(i) Since the value of Eochanges when the concentration of Cu2+increases?
(ii) The transformation of Cu2+to Cu become more or less viable when the concentration of Cu2+increases? Please indicate the reason(s).
Q.24 A first-order reaction has a half-life of 1.15 × 104
s.
How long does it take to complete 99% of the reaction?
2
Q.25 Esterification of a carboxylic acid with an alcohol in the presence of a mineral acid such as
The catalyst is a reversible reaction.
(i) Suggest two things that can be done with the products formed to drive the reaction inward.
the forward direction.
(ii) When one mole of acetic acid and one mole of ethanol reach equilibrium
at 298 K, how many moles of ethyl ethoxide and acetic acid are in it?
¿Balance? (Suponiendo Kc = 4 a 298K)
2
Chemistry Class 12 of 2023 Bonus Practice Questions:SECTION C
This section contains 5 questions with an internal choice of two questions. The following questions are of the short answer type and are worth 3 points each.
Q.26 (a) Is benzaldehyde less or more reactive towards electrophilic substitution reactions than benzene (C6H6)? Justify your answer.
(b) Indicate the position on the ring where electrophilic substitution is likely to predominate in benzaldehyde. Explain why.
(c) Between 2-methyl-butan-2-ol and 2-methyl-butan-1-ol that cannot be made by reduction of an alcohol or aldehyde? Why?
P.27 In the 20th century, the German scientist Werner managed to elucidate the structures of the five compounds platinum, chlorine and ammonia. Some of the properties of these compounds are shown in the following table.
(i) What is the oxidation state and coordination number of Pt in compound C?
(ii) Which of the complexes formed by compounds A, B, C and D have structural isomers?
(iii) Predict the shape of each compound.
Q.28 Suman drank two glasses of water from a water filter. He chills one cup in the fridge and heats the other on the stove. Which glass of water contains more dissolved oxygen? Explain the use of Henry's law.
P.29 The image below shows the effect of acid and base on aqueous ethylamine.
(a) What evidence is there for a chemical reaction between ethylamine and hydrochloric acid?
(b) Why does the odor of ethylamine disappear when hydrochloric acid is added?
(c) Why does the ethylamine odor reappear when sodium hydroxide is added?
Q.30 A mixture of 0.5 mol of acetaldehyde and 0.5 mol of diethylketone is treated with 1 mol of sodium cyanide (NaCN). What will be the main product of this reaction? Give two reasons for your answer.
O
(a) Show the steps required to convert nitrobenzene to phenol.
(b) The following table shows the observation when sodium reacts with ethanol and phenol.
(i) The reaction in each case involves the reduction of the hydrogen ion by sodium. Write an ionic reaction for both cases.
(ii) Which acid is stronger, phenol or ethanol? Why?
Chemistry Class 12 of 2023 Bonus Practice Questions:SECTION D
This section contains two questions and is worth 4 points each.
F.31 The following image shows the double helix structure of DNA. 4
(i) The double helix structure is easily destroyed by changing (a) the temperature and (b) the pH. Explain the reason for both cases.
(ii) Suppose the bonds holding the DNA strands together for the double helix were (a) covalent bonds (b) London dispersion forces. What would be the problem in each case?
Q.32 During a titration, 240 ml of NaOH completely reacted with 100 ml of H2SO4 solution. The weight of H2SO4 removed was 9.8 g.
i) What is the molarity of the NaOH used?
ii) Calculate the amount of NaOH dissolved in the solution.
iii) How many grams of NaOH must be added to the original NaOH solution to make 1 liter of 0.5 M NaOH solution?
(The molar mass of NaOH is 40 g/mol and the molar mass of H2SO4 is 98 g/mol.)
Chemistry Class 12 of 2023 Bonus Practice Questions:SECTION E
Each question is worth 5 points. Read the text or the group image carefully and answer the following questions.
P.33 One of the most commonly used batteries in our daily lives is Duracell, also known as an alkaline battery. The image below shows the internal structure of a Duracell.
This cell uses a zinc half cell and another half cell containing a carbon (graphite) electrode in contact with wet manganese oxide. Assuming the electrode potential for Zn2+/Zn= -0.76 V and Mn4+/Mn3+ (ac.) = +0.74 V.
(i) Write down the half-cell responses for that cell at each electrode.
(ii) Calculate the total potential of the cell.
(iii) Which of the two will be the positive electrode and why?
(iv) Draw a diagram of the cell showing the direction in which the reaction takes place in that cell.
O
Imagine that you are in a chemistry laboratory and the professor is explaining the electrolysis of a CuSO4 solution and the products released after electrolysis. The professor made two adjustments for the electrolysis process. In setup I, the electrolysis of the CuSO4 solution is performed with Pt electrodes and in setup II, the electrolysis of the CuSO4 solution is performed with copper electrodes. Based on this, answer the following questions:
i) In which configuration I or II does the color of the CuSO4 solution disappear and why?
ii) Write down the chemical reaction that takes place at the Cu anode in configuration II.
iii) Name the product obtained at the anode in configuration I.
iv) Which of configurations I or II represents the refining of raw copper?
Q.34 The image below shows the boiling point of the first seven straight-chain primary alcohols and the first seven straight-chain primary alkanes. The boiling point of both series increases monotonically with increasing molecular size. However, the slope of the increase is different for both series. Look at the graph above and answer the following questions:
(i) Why is the boiling point of alcohols higher than that of the corresponding alkanes?
(ii) Why do the boiling point differences between alcohols and the corresponding alkanes decrease as the number of carbon atoms increases?
(iii) Can the two graphs intersect?
(iv) If the boiling point is replaced by the melting point, will the graph look almost the same?
(v) What is the boiling point diagram for straight chain primary amines versus alcohols and alkanes?
Q.35 i) Give the electronic configuration of the outer shell of an element with atomic number 24. Why is it different from neighboring elements on the periodic table?
ii) Why is Hg not considered a transition element?
iii) The third enthalpy of ionization of some transition elements is given below:
Explain the reason for the break in the third constantly increasing enthalpy of ionization, as shown in the table. Based on this, what can be said about the second ionization energy of Cr compared to that of Mn?
Grade 12 Chemistry Extra Practice Questions 2023 PDF Download Link
Below is the download link for the Chemistry extra practice questions of Class 12 2023 in PDF format:
Grade 12 Chemistry Extra Practice Questions 2023 PDF Download Link
Grade 12 Chemistry Bonus Practice Questions - Prior Year
SECTION A
1. In the chemistry lab, Zoya built an electrochemical cell as shown below:
At room temperature, he found the initial reading on the voltmeter to be +0.16V.
(i) The standard electrode potential for the Cu2+/Cu electrode is given by
Cu2+(aq) + 2e– → Cu(s); Eo = + 0.34 V
Calculate the potential of the electrode to the left of the electrochemical cell above.
(ii) Give the direction of the current in the cell above. What will be the emf of the cell if the concentration in the beaker on the left is increased to 1 mol dm-3?
2. (a) An aldehyde was generated upon hydration of an alkyne P in the presence of H2SO4 and HgSO4. Identify the alkyne P
(b) Arrange the following compounds in increasing order of electrophilicity of the carbonyl carbon atom.
CH3CH2-CHO, CH3CH2-CO-CH3, HCHO, CH3-CO-CH3
3. Answer two of the following questions.
(a) C6H5-CH2-CH2-CH2-C6H5 is heated with alkaline potassium permanganate and then the reaction mixture is made acidic with dilute hydrochloric acid. Name the resulting product.
(b) Goat o nombre IUPAC de HOOC – CH2CH2CH2CH2 -COOH.
(c) Arrange the following in increasing order of acidity:
4-chlorobenzoic acid, 4-nitrobenzoic acid, 4-methylbenzoic acid
SECTION B
4. A sample of benzaldehyde contains a small amount of a water-insoluble alcohol. Explain the steps of a chemical process to obtain pure benzaldehyde from the mixture.
5. (i) The molar conductivity curve versus √c for NaCl, HCl, and NH4OH is shown below in random order. Identify which graph corresponds to HCl, NaCl, and NH4OH.
(ii) Justify your answer in (i)
6. An R-CO-NH2-alkylamide is converted to an amine as follows:
(i) by reduction with LiAlH4
(ii) by treatment with bromine in alcoholic NaOH
(a) Classify the type of amine produced in the above procedures as primary, secondary, or tertiary.
(b) State one important difference in the amine products produced by the above two processes.
(c) What are the advantages of these two methods of producing an amine over producing an amine by treating an alkyl halide with alcoholic ammonia solution?
O
(a) Arrange the following amines in order of increasing basicity. Consider everything in a gaseous state.
C6H5NH2, NH3, (C2H5)2NH, 4-NitroC6H5NH2, C2H5NH2
(b) Name the factor that most influences the order of basicity of compounds in the gaseous state.
(c) Of the following two compounds, (ii) is more acidic than (i). Explain why.
(i) C6H5 – CO – NH – C2H5
(ii) C6H5 – SO2 -NH – C2H5
7. Richa uses a rough carbon surface instead of a flat surface to adsorb 'x' g N2 at room temperature (To). The Δadsorption was very low and positive.
(i) Why is a rough surface better than a flat surface for adsorption? (assuming all other variables are equal)
(ii) Is the adsorption physical or chemical? Justify your answer.
(iii) If x+20 g N2 adsorb at temperature T1, then compare To and T1
(i) The following table shows the volumes of nitrogen adsorbed by a 3 g sample of activated carbon at 0 °C:
| Pressure (mm) | 180 | 540 |
| Volumen (cm3/g) | 16.5 | 38.1 |
Evaluate the constants k and n if the above data fit the Freundlich adsorption isotherm.
(ii) Plot the adsorption temperature curve for the above case at p = 180 mm.
8. The following table shows the oxidation potential of some of the transition elements in the first row:
| Element | kr | Minnesota | confidence |
| Eo(M2+/M) | -0,9 V | -1.18V | -0,4 V |
| Eo(M3+/M2+) | -0,41 V | +1,57V | +0,8 V |
Based on the above data,
(i) Why is the value of Eo so much more positive for the pair Mn3+/Mn2+ than for
¿Cr3+/Cr2+ o Fe3+/Fe2+?
(ii) Arrange these items in descending order of their ease of oxidation.
(iii) Comment on the comparative stability of Fe3+ and Mn3+ in acidic solutions.
9. Answer the following:
(i) Arrange Ti3+, Cr3+, Ni3+, Cu+1 in increasing order of their magnetic moments.
(ii) Explain why zinc has the lowest melting point in the 3d series.
(iii) Although Mn in KMnO4 has the d0 configuration, it imparts color. explain the reason
behind.
10. Justify the following:
(i) Both [FeF6] 3- and [CoF6] 3- contain F6 as a ligand, but the former is a colorless compound and the latter is coloured.
(ii) [Co(NH3)6] 3+ is diamagnetic while [CoF6] 3– is paramagnetic in nature.
(iii) Zn2+ is colorless while Cu2+ is colored.
(a) Ti3+ forms a complex in aqueous solution and can absorb light with a wavelength of 5000 Å. Name a ligand that would form a titanium(III) complex such that this complex can absorb light with a wavelength less than 5000 Å. Similarly, name a ligand that would form a titanium(III) complex such that the complex can absorb light with a wavelength greater than 5000 Å.
(b) Arrange the metal ions of the following compounds in order of decreasing pure spin magnetic moments:
[V(CN)6] 4–, [Fe(CN)6] 4–, [Ru(NH3)6] 3+ y [Cr(NH3)6] 2+
11. Show how aniline can be converted to 4-bromoiodobenzene. (List all steps involved.)
O
(a) Give the IUPAC name and structure of the product obtained from the reaction of ethanamine and benzoyl chloride.
(b) Can the product obtained in (a) undergo the Hoffmann degradation reaction? If so, write down the structure of the resulting product. If not, explain why.
SECTION C
An important goal for the food scientist is to predict the change in quality of a given food as a function of time and environmental conditions. This has become the focus of many research and development projects, as the information obtained is necessary for professionals in the food industry to set an open date for the food on the package (z" date) so that consumers are aware of it. more informed when handling the product. To make useful predictions about shelf life, the researcher needs information about the kinetics of the reactions that lead to quality or nutritional loss depending on the reaction phase conditions in the food and in the external environment. Some general types of food spoilage are:
(1) Microbial spoilage of foods: the reference population burden and the end point in terms of toxin levels or the maximum allowable number of organisms are needed to make predictions about the change in microbial concentration levels over time. weather. There are many data in the literature for microbial growth rate constants under specific conditions. To monitor this type of food spoilage, the Food Corporation of India (FCI) states that the concentration of a microorganism in a given can would be unacceptable with a maximum change of +30% from the microorganism baseline.
(2) Senescence: Once a plant is harvested or an animal is slaughtered, the tissues are deprived of any external sources of carbon or nitrogen and therefore use their internal carbohydrates, proteins, or fats as a source of energy. They do this by continuing their normal enzymatic reactions in an aging process commonly known as senescence. Eventually, the energy sources run out or the end products accumulate and render the food inedible. A well-known example of this process is the loss of sweetness in ears of corn during storage. Studying the rates of these aging responses is important to the processor who wants to ensure quality ingredients in processed foods. It is also important for the supplier of fresh products
(3) Enzymatic Chemical Deterioration: When a food is processed in any way (heated, salted, dried, frozen, etc.), its internal structures are destroyed, damaging the membranes. This destroys the tightly compartmentalized system and allows the normally separated chemicals to come into contact and react. These reactions then become the main causes of quality loss. As mentioned above, many of the chemical reactions that lead to quality degradation also lead to physical changes, such as reduced solubility (NEB, oxidation) or softness (enzymatic reaction, ageing). Therefore, a physical property can be used as a quality index and its change over time can be treated kinetically. Other physical responses include almost all-or-none phenomena (ice thawing or fat melting) or an increase in velocity when the temperature decreases instead of increasing, a situation inaccessible to most simple kinetic models. An example of the former is the sudden loss of crispness in snacks or dry cereals when they absorb moisture and reach a certain water activity. The second type is represented by the deterioration of some frozen foods due to the acceleration of the concentration and the damage of the membrane with the decrease in temperature, and by the physical aging of the bread, which hardens faster compared to the temperature when stored refrigerated.
(Source: Application of Chemical Kinetics to Food Spoilage T. P. Labuza Department of Food Science and Nutrition, University of Minnesota, St. Paul, MN 55108)
12. (i) If the manufacturing date of a canned food is June 1, 2021, what is the expiration date of this food according to the FCI mandate? (Assume the average microbial decay rate constant is 2 units day-1)
(ii) The Department of Archeology uses kinetic theory to determine the age of plants/trees. The department found a rare tree artifact that contained only 80% of the 14C found in the living tree. Find the age of the sample when t1/2 of 14C is 5730 years.
(iii) Plot the change in the level of the food quality index (factor) as a function of time for zero-order and first-order reactions.
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FAQs
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It is with their expertise, guidance and keen eye for details that the content in each offering from Oswaal Books meets highest quality standards. No wonder, Oswaal Books holds an enviable place in every student's heart!
What is the most important question in chemistry? ›The most important question in chemistry is "Where are the electrons?" electronegative atoms (e.g. F, Cl, O, N) of a molecule. The electronegative atoms pull electron density away from the less electronegative atoms (e.g. C, H) to which they are bonded.
Is CBSE 12 chemistry paper easy? ›On other hand paper of chemistry was easy. Overall, the paper can be said a moderate one," Ms Sharma said. "The students did not face any issues w.r.t time management and they all could complete the paper within the stipulated time. All questions were doable and similar to the sample papers practiced in class.
Is PYQ enough for chemistry? ›We can't say it is enough. Previous year question papers are good for practice. For concepts you should prefer reference books.
How do you score 120 in chemistry? ›- Timetable: By making a timetable for your preparation, you plan it all down to the last bit. ...
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Which topic-wise sample paper is better for class 12 maths, Arihant or Oswal? I would recommend Oswaal Books Question Bank and Sample Question Papers. It contains Chapterwise and Topicwise presentation for systematic and methodical study. They are detailed in nature.
Which is better Arihant or Oswal Class 12? ›Both Arihant and Oswaal are good but comparing them, Oswaal has a better range of questions. They also provide you with the best answer along with the toppers answers. They also provide the previous years papers. It will also help you understand the style of questioning of the board.
How can I get 95 in Class 12 science? ›- Compete with yourself: ...
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Answer: which has more calories : table sugar or aspartame ?
What is the easiest way to memorize chemistry? ›- Review and Study Material Before Going to Class. ...
- Seek Understanding. ...
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Which topic from chemistry has the highest weightage? ›
The weightage of organic chemistry remains constant almost every year and is the highest of all the 3 sections.
Which board is very easy? ›The CBSE Board syllabus is far easier compared to ICSE. The CBSE syllabus features an additional compact structure and fewer subjects.
Is NCERT and PYQ enough for CBSE 12? ›NCERT books are fundamental books of the CBSE Board. These books have all the information that is required by any CBSE student of classes 10 and 12. These books are being read by all CBSE Board students since class 6th, which is why it is easy to follow and understand the language of these books.
Which is the easiest board for Class 12? ›Question: Which board is the easiest in India? Answer: The syllabus of the CBSE Board is considered as quite comprehensive and easy to understand.
How do you get 150 marks in chemistry? ›- For Inorganic chemistry----> Learn and revise all the reactions from Ncert only. It is enough to get good marks.
- For Organic chemistry-------> Learn all the name reactions from Ncert. ...
- For Physical chemistry-----> Learn all the formulas and practice from ncert first and then from Reference books.
You should practice at least four full-length mock tests of Chemistry for your board exam. Go through the previous year papers and spend more time on the known difficult previous year questions. During the practice of mock exams, practice your response to panic.
How do you score 180 in chemistry? ›Answer: Nearly 15 questions are asked from all three, including physical, organic, and inorganic chemistry. Almost all questions asked are from NCERT class 11th and 12th. Answer: Take out at least two hours for revision every day.
How I got A * in chemistry A level? ›Complete understanding of the syllabus, outstanding problem-solving skills, excellent exam technique and a focused plan are the key elements of securing the top grade for A level chemistry. Achieving an A* in A Level chemistry is difficult – only around 1 in 10 students achieve this grade each summer.
Is Grade 12 chemistry hard? ›Chemistry is exceptionally hard in Grade 12! Once students gain confidence in Chemistry, it becomes a lot easier when they are taking Chemistry in University. If students scrape through Chemistry, they will then require serious tutoring in University, which is a lot more expensive than tutoring in high school.
What is the pass rate for chemistry? ›| AP Class/Exam | Pass Rate (3 or Higher) | Perfect Score (5) |
|---|---|---|
| AP Chemistry | 56.1% | 10.6% |
| All AP Classes | 71.13% | 19.57% |
Who is the owner of Oswaal? ›
Its foundation seeds were laid by late Mr. Padam Chand Jain in 1950 by the name of “Ratan Prakash Mandir”. Later, the seeds were nurtured into a young fruitful tree by his son Mr. Naresh Jain who named it as Oswaal Books in 1984 and started providing guidebooks and sample papers to students across the country.
Is Oswaal or Xam idea good? ›Both the books Oswal and exam idea are good. Oswal is good because it includes the following points. 1) It includes both the sample papers and question bank for the exam. 2) It includes points with the revised syllabus of CBSE and with covering all the topics related to the subject.
Who owns Oswaal? ›Jawahar Lal Oswal, the present Chairman and Managing Director. The Board comprises of ten directors including three promoters directors namely Sh. Jawahar Lal Oswal, Sh. Kamal Oswal, Sh.
Is Arihant better than NCERT? ›Both the books are very good, Hoever Arihant NCERT books are more recommended as they contain relevant problems and saves time and is more appealing to majority of JEE aspirants.
Which guide is best for 12? ›- SaraS Publications.
- Sherlyn Publication.
- Sri Ganga Publications.
- Sudarshan Publication.
- Sura Publications.
- Surya Publications.
- Twinkle Publications.
- Way To Success Publications.
| Subject | Best Reference Books For Class 12 |
|---|---|
| ENGLISH CORE | Flamingo Vistas Oswaal CBSE Sample Question Paper Class 12 English Core Book |
| MATHEMATICS | Text book Part I , Part II XII Oswaal CBSE Sample Question Papers Class 12 Mathematics Book |
You don't need to worry. 80% is not a bad percentage. I know in this years where everyone scores very high percentile you will feel depressed. There is no gain if you loose your self confidence comparing your results with others.
Is 75 percent good in class 12? ›Getting into a prestigious college in India usually requires a high board percentage; if entrance exams are criteria, then a minimum cutoff of 60 or 75 percent is usually put by universities and institutes.
What should I do if I got 60% in 12th? ›Re: What should I do after scoring 60% in 12th science? u can go in for engineering which would be the best option if u want to earn big..else u can do a computer course and get yourself placed in a decent job in some company..but if u want a secure future..then better to go in for engineering..
Is Chem the hardest science? ›Chemistry isn't merely a challenging science major; CollegeVine ranked it the most difficult of all the majors in its rankings of The 10 Easiest and 10 Hardest College Majors.
Which part of chemistry is the hardest? ›
- Physical Chemistry is the hardest branch of chemistry.
- It involves the study of physical properties and constitution of matter, the laws of chemical combination, and theories governing chemical reactions.
One of the hardest known substances is Diamond. Diamond is simple pure Carbon in a unique physical arrangement.
What is the best time to study chemistry? ›That said, science has indicated that learning is most effective between 10 am to 2 pm and from 4 pm to 10 pm, when the brain is in an acquisition mode. On the other hand, the least effective learning time is between 4 am and 7 am.
How can I memorize 10 times fast? ›- Try to understand the information first. Information that is organized and makes sense to you is easier to memorize. ...
- Link it. ...
- Sleep on it. ...
- Self-test. ...
- Use distributed practice. ...
- Write it out. ...
- Create meaningful groups. ...
- Use mnemonics.
- Syllabus.
- Basic Concepts of Chemistry.
- Structure of an Atom.
- Classification of Elements and Periodicity in Properties.
- Chemical Bonding and Molecular Structure.
- States of Matter: Gases and Liquids.
- Chemical Thermodynamics.
- Equilibrium.
One of the most difficult concepts in chemistry for students to grasp is that the entirety of the course is based on the behavior of matter. We talk about matter typically at the molecular or atomic level not seen without advanced equipment.
Is 2023 board exam easy? ›CBSE Board exam 2023 is going to be super difficult!
It's estimated that almost 60% of the questions will be competency and subjective-based. Also, the number of case-based questions will increase and 20% of the questions on critical thinking will be included.
However, in the case of the ICSE Board, students encounter a comprehensive and practical-based syllabus to get an in-depth knowledge of the subject matter. This is one of the prime reasons why ICSE is the toughest board in India.
Which is the toughest board in world? ›1. Gaokao. The Gaokao is a college admission exam in China that is famed for being one of the top ten most difficult exams in the world. Due to the difficulty of the exam, some European and American colleges have begun to accept Gaokao marks.
Is CBSE 12th tougher than state board? ›It is more difficult to study for CBSE exams than for State exams. For Engineering and Medical, the entrance exams are based on the CBSE syllabus, so if your child wishes to study in a top institution such as IIT or AIIMS, CBSE is certainly the best way to go.
What is CBSE best of 5 rule? ›
The CBSE board has a best of five rule in which your main percentage is decided by one language subject I.e. English and other 4 subjects in which you get high scores . And the remaining subjects becomes additional whose marks won't be added to your main percentage.
Can I pass in 12th exam just by reading NCERT solutions? ›Ans. Yes, ncert books are enough for CBSE exams even cbse suggest to read from ncert books only.
Is 1 month enough for 12th boards? ›Because As per the syllabus of the 12th board exam, this one month is not enough, but with this latest revised exam pattern, you will have to prepare for fifty per cent of this total syllabus at a time. So if you want to get a good score, you have to ensure that you do not deviate from the aim for even a single hour.
How many hours should I study for 12 boards? ›Prepare a Timetable
It is important to decide how many hours you should study in Class 12. You must prepare a timetable for your studies and utilize your time in the best possible way. Devoting 6-8 hours a day for studies is the best timetable for Class 12.
Considered one of the toughest exams in India, the GATE syllabus comprises the concepts taught during the 4 years of the undergraduate degree. It is organised as an online exam and evaluates test-takers on two parameters, i.e. General Aptitude and knowledge of Technical and Engineering Mathematics.
How do you get full marks in A level chemistry? ›Complete understanding of the syllabus, outstanding problem-solving skills, excellent exam technique and a focused plan are the key elements of securing the top grade for A level chemistry. Achieving an A* in A Level chemistry is difficult – only around 1 in 10 students achieve this grade each summer.
How can I get high marks in chemistry? ›- Review and Study Material Before Going to Class. ...
- Seek Understanding. ...
- Take Good Notes. ...
- Practice Daily. ...
- Take Advantage of Lab Time. ...
- Use Flashcards. ...
- Use Study Groups. ...
- Break Large Tasks Into Smaller Ones.
- Knowing the syllabus thoroughly.
- 2) Plan your schedule.
- 3) Comprehend the Topics.
- 4) Practice Sample Papers.
- 5) Practice Previous Year Papers.
- 6) Consider extra help.
- 7) Prepare from Coursebooks.
- 8) Avoid Distractions.
- Write Down What You Know. Don't risk drawing a blank when confronted with a calculation! ...
- Read the Instructions. Read the instructions for the test! ...
- Preview the Test. ...
- Read Each Question Completely. ...
- Answer Questions You Know. ...
- Show Your Work.
This approach means that as long as a student achieves enough marks at subject level (76 or more in this example), they will receive an A* grade. It doesn't matter how they get their 76 marks. One student could score full marks (60/60) on paper 1 and 16/40 marks on paper 2 (60+16=76).
Is 80% an A at A Level? ›
The A* at A Level is awarded to candidates who achieve a grade A on the A Level overall (80%), and who also achieve at least 90% on the uniform mark scale (UMS) across their A2 units.
How many people get a * s at A Level? ›On that measure, results overall are higher than pre-pandemic levels, with the proportion of As and A*s up from 25.4% in 2019 to 36.4%, and in the three years since exams were last sat the share of A*s has gone up by almost seven percentage points, from 7.7% to 14.6%.
Why am I struggling in chemistry? ›The primary reason chemistry is so hard is because of the topic progression. You really have to fully understand several topics before you can fully understand other topics. It's important to keep in mind, memorization isn't the key here. There's a certain element of memorization.
How many hours should I sleep in class 12 science? ›You must have a sleep of 6 to 8 hours while studying for class 12 exams. If you don't take adequate sleep while studying then you may not only feel drowsiness, but you will also not be able to concentrate in the class properly.
How can I get 95 in 12 class? ›- Compete with yourself: ...
- Make textbooks your bible: ...
- Solve sample papers religiously: ...
- Keep a check on your handwriting: ...
- Don't neglect English: ...
- Stop studying 12 hours before the exam:
Insufficient Math Preparation
You will need to be able to perform unit conversions. Expect to work chemistry problems on a daily basis. Don't rely too much on a calculator. Chemistry and physics use math as an essential tool.
Organic Chemistry:
It shouldn't surprise you that organic chemistry takes the No. 1 spot as the hardest college course. This course is often referred to as the “pre-med killer” because it actually has caused many pre-med majors to switch their major.
One of the most difficult concepts in chemistry for students to grasp is that the entirety of the course is based on the behavior of matter. We talk about matter typically at the molecular or atomic level not seen without advanced equipment.