Class 12 Chemistry Additional Practice Questions 2023
CBSE Class 12 Chemistry Practice Questions 2023 will help students to score well in their CBSE Exam 2023. Recently, the Central Board of Secondary Education released the CBSE Class 12 Chemistry Practice Questions 2023 on its official website at https://cbseacademic.nic.in/. The students appearing in CBSE Exam 2023 must go through all the CBSE Class 12 Chemistry Practice Questions 2023 given on this page and bookmark this page to get the latest updates from the Central Board of Secondary Education.
CBSE Class 12th Chemistry Additional Practice Questions
To score full marks in Class 12 Chemistry the candidates must practice CBSE Class 12 Chemistry Practice Questions 2023 given on this page and consolidate all the formulas, chemical reactions and concepts of chemistry given in the CBSE Syllabus. The students must solve CBSE Class 12 Chemistry Practice Questions 2023 to assess their preparation for Chemistry for the CBSE Exam 2023.
Class 12 Chemistry Additional Practice Questions 2023: General Instructions
Subject: CHEMISTRY (043)
Maximum marks: 70
Time Allowed: 3 hours
General instructions:
Read the following instructions carefully.
a) There are 35 questions in this question paper with internal choice.
b) SECTION A consists of 18 multiple-choice questions carrying 1 mark each.
c) SECTION B consists of 7 very short answer questions carrying 2 marks each.
d) SECTION C consists of 5 short answer questions carrying 3 marks each.
e) SECTION D consists of 2 long answer questions carrying 4 marks each.
f) SECTION E consists of 3 long answer questions carrying 5 marks each.
g) All questions are compulsory.
h) Use of log tables and calculators is not allowed
Class 12 Chemistry Additional Practice Questions 2023: SECTION A
The following questions are multiple-choice questions with one correct answer. Each question carries 1 mark. There is no internal choice in this section.
Q.1 De-icing is the process of removing snow, ice or frost from a surface. In extremely cold regions, car windows get covered by ice reducing the visibility. The image below shows the de-icing of the window of a car during extreme cold using a fluid. Which of the following compounds could be present in the de-icing fluid used above?
A. formaldehyde
B. phenol
C. propan-2-ol
D. acetic acid
Q.2 Which of the following reaction mechanism is not involved in the given reaction sequence?
A. free-radical substitution
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 based on 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 was conducting an experiment to figure out the rate equation of the following reaction:
2 NO + O2 –> 2 NO2
He measured the rate of this reaction as a function of initial concentrations of the reactants as follows:
Which of the following could be a reason for the inconsistency in the initial rate of formation of NO2 data for experiment 4?
A. The rate of reaction does not depend on the concentration of the reactants.
B. Higher concentration of O2 could have resulted in slowing down the rate of reaction.
C. Higher concentration of NO could have resulted in slowing down the rate of reaction.
D. The temperature of the reactants in experiment 4 could have been different than for the other experiments.
Q.5 The image below shows 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 current source towards the solution at one electrode, and an equal number of electrons flow away from the 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. i and ii only
C. ii and iii only
D. all- i, ii, and iii
Q.6 For a certain reaction X, rate = 0.7ZABe-EA/RT. It is 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 the reactions involve complex molecules.
B. Both the reactions involve simple 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 formula [ML2](n−4)+ where L represents a bidentate ligand. Which of the following could be the charge on the ligand L?
A. -2
B. -1
C. 0
D. +2
Q.8 The image below shows different benzene derivates that give mononitration product at ortho, meta and para positions along with the rate of nitration relative to benzene. Which of the following row shows atleast one INCORRECT description about the reaction
A. only B
B. only C
C. only B and C
D. only C and D
Q.9 The rate constants of a reaction at 400 K and 600 K are 5 x 10-3s–1 and 8 x 10-3s–1 respectively. What extra piece of information is needed to calculate the value of A (frequency factor)? (According to the Arrhenius equation, 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 extra information is needed. A can be calculated with the information available]
Q.10The compound [Co(NH3)5Cl]SO4 is isomeric with the compound [Co(NH3)5SO4]Cl. Which of the following rows correctly represents the oxidation state of cobalt in these compounds? Rows [Co(NH3)5Cl]SO4 [Co(NH3)5SO4]Cl
A +2 +3
B +3 +2
C +2 +1
D +3 +3
A. A
B. B
C. C
D. D
Q.11The image below shows an experimental setup to prepare an organic product X. Which of the following could ‘X’ be?
A. ethane
B. ethene
C. ethanoic acid
D. diethyl ether
Q.12During protein synthesis in cells, amino acids condense (in the presence of enzymes) through the formation of the amide link (–CONH–), or peptide bond, to form a polypeptide chain, which then folds to form a biologically active protein. The equation below shows the formation of a dipeptide, Ala-Gly, formed by condensation of the two amino acids, alanine and glycine in a test tube. Which of the following statements is/are true for the above reaction?
(i) A dipeptide Gly-Ala is equally likely to be formed by condensation of alanine and glycine.
(ii) Water is eliminated in the above condensation reaction.
(iii) Oxygen and hydrogen is released as gases in the above condensation reaction.
A. i only
B. i and ii only
C. ii and iii only
D. all- i,ii, and iii
Q.13Zirconium (Zr, Atomic number 40) and Hafnium (Hf, Atomic number 72) are transition series metals of group 4. They are found together in nature and are difficult to separate from each other. Which of the following is the reason for the above?
A. The almost 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 the elements.
Q.14Which of the following would be among the products of the reactions between ammonia reacts with bromoethane?
(i) CH3CH2NH2
(ii) (CH3CH2)2NH
(iii) (CH3CH2)3N
(iv) (CH3CH2)4N+Br−
A. only i
B. only i and ii
C. only i, ii, and iii
D. all- i, ii, iii and iv
Q.15 Given below are two statements labelled as Assertion (A) and Reason (R).
Assertion (A): Dimethyl amine has higher boiling point than trimethyl amine.
Reason (R): The molecular mass of trimethyl amine is relatively higher than that of dimethyl amine.
Select the most appropriate answer from the options given below:
A. Both A and R are true and R is the correct explanation 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.16Given below are two statements labelled as Assertion (A) and Reason (R).
Assertion (A): A silver mirror can be created at the wall of a test tube using ethanal.
Reason (R): Ethanal can react with Fehling’s solution
Select the most appropriate answer from the options given below:
A. Both A and R are true and R is the correct explanation 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.17Given below are two statements labelled as Assertion (A) and Reason (R).
Assertion (A): At a constant temperature, the dissociation constant of chloroethanoic acid will be higher than that of propanoic acid.
Reason (R): Higher the number of carbon atoms in a compound, lower will be the dissociation constant.
Select the most appropriate answer from the options given below:
A. Both A and R are true and R is the correct explanation 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.18Given below are two statements labelled as Assertion (A) and Reason (R).
Assertion (A): At room temperature, propan-2-ol and 2-methylpropan-2-ol, when heated with acidified potassium dichromate, slowly turns the colour of orange dichromate to green.
Reason (R): Secondary and tertiary alcohols are readily oxidised to aldehydes which gets oxidised to acids.
Select the most appropriate answer from the options given below:
A. Both A and R are true and R is the correct explanation 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 false.
Class 12 Chemistry Additional Practice Questions 2023: SECTION B
This section contains 7 questions with internal choice in two questions. The following questions are very short answer type and carry 2 marks each.
Q.19At high temperatures, ethyl chloride produces HCl and ethylene by the following first order reaction:
CH3CH2Cl –> HCl + C2H4
In an experiment, when the initial concentration of ethyl chloride was 0.01 M, the rate of the reaction was found to be 1.6 x 10-8 M/s. What will be the rate of reaction if the initial concentration of ethyl chloride is 0.07 M?
Q.20Pineapple contains a protease enzyme that breaks down proteins. If you try to make a
jelly with fresh chunks of pineapple, the jelly won’t set but it would set if you use canned
pineapple. Explain.
OR
The chain structure of Lysine is shown below.
(i) Based on the structure, is Lysine acidic, basic, or neutral overall? Explain.
(ii) What will be the structure of lysine if it is placed in a solution of pH value as 1?
Q.21 2-bromooctane reacts with alcoholic NaOH to give 2-octanol as shown below.
(a) Identify the type of substitution reaction mechanism. Justify your answer.
(b) What effect will it have on the rate of the reaction if:
(i) the concentration of NaOH is reduced by half?
(ii) the concentration of 2-bromooctane is reduced by half?
OR
(a) Which of the following two compounds has a chiral centre?
(b) Two compounds X and Y are enantiomers of each other.
Name one 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 whereas [CoCl4]2- does not show geometrical isomerism and has no isomers why?
(ii) When NaOH solution is added to aqueous copper (II) sulphate solution, hydroxide ions displace water molecules forming a pale blue precipitate, X. If excess ammonia is now added, water molecules and hydroxide ions are exchanged by ammonia molecules, forming a deep blue solution, Y. Identify X and Y.
Q.23The half equation for a redox reaction represents an equilibrium between two sides of an equation such as:
Cu2+ (aq) + 2e- —> Cu (s); Eo= +0.34 v
(i) How will the value of Eo change if the concentration of Cu2+ increases?
(ii) Will the conversion of Cu2+ to Cu become more or less feasible if the concentration of Cu2+ increases? Give reason(s).
Q.24A first order reaction is found to have a half-life of 1.15 × 104
s.
What will be the time required for completion of 99% of the reaction?
2
Q.25Esterification of a carboxylic acid with an alcohol in the presence of mineral acid as
catalyst is a reversible reaction.
(i) Suggest two things that can be done with the products formed to push the reaction in
the forward direction.
(ii) If one mole of ethanoic acid and one mole of ethanol are allowed to reach equilibrium
at 298K, how many moles of ethyl ethanoate and ethanoic acid are present at
equilibrium? (Assume Kc = 4 at 298K)
Class 12 Chemistry Additional Practice Questions 2023: SECTION C
This section contains 5 questions with internal choice in two questions. The following questions are short answer type and carry 3 marks each.
Q.26 (a) Is benzaldehyde less or more reactive to electrophilic substitution reactions than benzene (C6H6)? Give an explanation for your answer.
(b) State the position on the ring at which electrophilic substitution is likely to predominate in benzaldehyde. Explain why.
(c)Between 2-methyl-butan-2-ol and 2-methyl-butan-1-ol, which cannot be produced by the reduction of either an alcohol or an aldehyde? Why?
Q.27 In 20th century, German scientist Werner succeeded in clarifying the structures of the five compounds consisting of platinum, chlorine, and ammonia. Some of the properties of these compounds are shown below in the table.
(i) What is the oxidation state and coordination number of Pt in compound C?
(ii) Which of the complexes formed for the compounds A, B, C, and D have structural isomers?
(iii) Predict the shape of each compound.
Q.28Suman took two glasses of water from a water filter. She cools one glass in a fridge and warms the other glass on a stove. Which glass of water will hold more dissolved oxygen? Explain using Henry’s law.
Q.29The image below shows the effect of acid and base on the aqueous ethylamine.
(a) What evidence is there for a chemical reaction between ethylamine and hydrochloric acid?
(b) Why does the smell of ethylamine disappear when hydrochloric acid is added?
(c) Why does the smell of ethylamine reappear when sodium hydroxide is added?
Q.30A mixture of 0.5 moles acetaldehyde and 0.5 moles diethyl ketone is treated with 1 mole of sodium cyanide (NaCN). What will be the major product in this reaction? Give two reasons for your answer.
OR
(a) Show steps to convert nitrobenzene to phenol.
(b) The table below shows the observation when sodium reacts with ethanol and phenol.
(i) The reaction in each case involves reduction of hydrogen ion by sodium. Write down an ionic reaction for both the cases.
(ii) Which is stronger acid- phenol or ethanol? Why?
Class 12 Chemistry Additional Practice Questions 2023: SECTION D
This section contains two questions and carry 4 marks each.
Q.31The image below shows the double helix structure of a DNA. 4
(i) The double helix structure is easily destroyed by change in (a) temperature and (b) pH value. Explain the reason for both the cases.
(ii) Suppose the bonds holding the DNA strands for double helix together were (a) covalent bonds (b) London dispersion force. What would be the problem in each case?
Q.32During a titration, 240 ml of NaOH reacted completely with 100 ml of H2SO4 solution. The weight of H2SO4 taken was 9.8 g.
i) What is the molarity of the NaOH used?
ii) Calculate the amount of NaOH dissolved in solution.
iii) How many grams of NaOH should be added to the original NaOH solution to make one litre of 0.5M NaOH solution?
(Molecular mass of NaOH is 40g/mol and molecular mass of H2SO4 is 98 g/mol.)
Class 12 Chemistry Additional Practice Questions 2023: SECTION E
Each question carries 5 marks each. Read the group text or image carefully and answer the questions that follow.
Q.33One of the most common cells that’s been used in our daily life is Duracell, also known as an alkaline cell. 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 of moist manganese oxide. Given that the electrode potential for Zn2+/Zn= -0.76 V and Mn4+/Mn3+ (aq.) = +0.74V.
(i) Write down the half-cell reactions for this cell at each electrode.
(ii) Calculate the overall cell potential.
(iii) Which of the two will be the positive electrode and why?
(iv) Draw the cell diagram, representing the direction in which reaction occurs in this cell.
OR
Imagine you are in a chemistry lab and the teacher is explaining the electrolysis of CuSO4 solution and the products liberated after electrolysis. The teacher made two Setups for the electrolysis process. In Set up-I electrolysis of CuSO4 solution is done by using Pt electrodes and in Set up-II electrolysis of CuSO4 solution is done by using Cu electrodes. Answer the following questions based on this:
i) In which Set up I or II will the colour of CuSO4 solution fades away and why?
ii) Write the chemical reaction taking place at the Cu anode in Set up II.
iii) Name the product obtained at the anode in Set up I.
iv) Which out of Set up I or II depict refining of crude copper?
Q.34The image below shows the boiling point of first seven straight chain primary alcohols and first seven straight chain primary alkanes. The boiling point of both the series increase monotonically with increasing size of the molecules. However, the slope of increment is different for both the series. Observe the above graph and answer the following questions:
(i) Why are the boiling point of alcohols higher than that of corresponding alkanes?
(ii) Why do the differences in boiling point between corresponding alcohols and alkanes get less as the number of carbon atoms increase?
(iii) Can the two graphs ever intersect?
(iv) Will the graph look like almost the same if boiling point is replaced with melting point?
(v) How will the boiling point graph for straight chain primary amines fare as compared to alcohols and alkanes?
Q.35 i) Write the outer shell electronic configuration of an element with atomic number 24. Why is this different from the elements that are adjacent to it in the periodic table?
ii) Why is Hg not considered as a transition element?
iii) The third ionisation enthalpy of a few transition elements are given below:
Explain the reason for the break in the trend of steady increase in third ionisation enthalpy as shown in the table. Based on this, what can be said about the second ionisation energy of Cr as compared to that of Mn?
Class 12 Chemistry Additional Practice Questions 2023 pdf download link
Below is the Class 12 Chemistry Additional Practice Questions 2023 pdf download link:
Class 12 Chemistry Additional Practice Questions 2023 pdf download link
Class 12 Chemistry Additional Practice Questions: Previous year
SECTION A
1. In the chemistry lab, Zoya set up an electrochemical cell as shown below:
At room temperature, she found that the initial voltmeter reading was +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 electrode potential of the electrode on the left-hand side of the above electrochemical cell.
(ii) Indicate the direction of current in the above cell. Also, what will be the emf of the cell if the concentration of the beaker on the left side is raised to 1 mol dm-3?
2. (a) An aldehyde was produced on the hydration of an alkyne P in the presence of H2SO4 and HgSO4. Identify the alkyne P.
(b) Arrange the following compounds in the increasing order of electrophilicity of the carbon atom of the carbonyl group.
CH3CH2-CHO, CH3CH2-CO-CH3, HCHO, CH3-CO-CH3
3. Answer any two of the following questions.
(a) C6H5-CH2-CH2-CH2- C6H5 is heated with alkaline potassium permanganate and the reaction mixture is then acidified with dilute hydrochloric acid. Name the product that will be formed.
(b) Give the IUPAC name of HOOC – CH2CH2CH2CH2 -COOH.
(c) Arrange the following in the 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 involved in a chemical method to obtain pure benzaldehyde from the mixture.
5. (i) The molar conductivity vs √c curve for NaCl, HCl, and NH4OH are shown below in random order. Identify which graph corresponds to HCl, NaCl, and NH4OH.
(ii) Give reasons to justify your answer in (i)
6. An alkyl amide R-CO-NH2 is converted to an amine in the following ways:
(i) by reduction with LiAlH4
(ii) by treating with bromine in alcoholic NaOH
(a) Classify the type of amine produced in the methods above as primary, secondary or tertiary.
(b) State one major difference in the amine products produced in the two methods above.
(c) What advantages do these two methods of producing an amine have over producing an amine by treating an alkyl halide with alcoholic ammonia solution?
OR
(a) Arrange the following amines in the increasing order of basicity. Consider all to be in the gaseous state.
C6H5NH2, NH3, (C2H5)2NH, 4-nitroC6H5NH2, C2H5NH2
(b) Name the factor that exerts the most influence on the order of basicity of the compounds when 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 charcoal surface instead of a flat surface to adsorb ‘x’ g of N2 at room temperature (To). ΔHadsorption was found to be very low and positive.
(i) Why is a rough surface better than a flat surface for adsorption. (assume all the other variables are the same)
(ii) Is the adsorption physical or chemical? Give a reason for your answer.
(iii) If x+20 g of N2 is adsorbed at temperature T1, then compare To and T1
(i) The table below shows the volumes of nitrogen adsorbed by a sample of 3g of activated charcoal at 0°C:
| pressure (mm) | 180 | 540 |
| volume (cm3 /g) | 16.5 | 38.1 |
Evaluate the constants k and n if the above data fits Freundlich’s adsorption isotherm.
(ii) Draw the adsorption vs temperature curve for the above case at p= 180 mm.
8. The table below shows the oxidation potential for some of the first-row transition elements:
| Element | Cr | Mn | Fe |
| Eo(M2+/M) | -0.9 V | -1.18 V | -0.4 V |
| Eo(M3+/M2+) | -0.41 V | +1.57 V | +0.8 V |
Based on the above data,
(i) Why is the Eo value for Mn3+/Mn2+ couple much more positive than that for
Cr3+/Cr2+ or Fe3+/Fe2+?
(ii) Arrange these elements in the decreasing order of their ease of getting oxidized.
(iii) Comment on the comparative stability of Fe3+ and Mn3+ in acid solutions.
9. Answer the following:
(i) Arrange Ti3+, Cr3+, Ni3+, Cu+1 in the increasing order of their magnetic moments.
(ii) Give the reason behind Zinc having the lowest melting point in the 3d series.
(iii) Although Mn has d0 configuration in KMnO4, it imparts color. Explain the reason
behind this.
10. Give reasons for the following:
(i) Both [FeF6] 3- and [CoF6] 3- contain F6 as ligands but the former is a colorless compound and the latter is colored.
(ii) [Co(NH3)6] 3+ is diamagnetic whereas [CoF6] 3– is paramagnetic in nature.
(iii) Zn2+ is colorless whereas Cu2+ is colored.
(a) Ti3+ in an aqueous solution forms a complex and can absorb light of wavelength 5000 Å. Name one ligand which would form a titanium(III) complex such that this complex can absorb light of lower wavelength than 5000 Å. Similarly, name one ligand which would form a titanium(III) complex such that this complex can absorb light of higher wavelength than 5000 Å.
(b) Arrange the metal ions of the following compounds in the descending order of spin only magnetic moment:
[V(CN)6] 4–, [Fe(CN)6] 4–, [Ru(NH3)6] 3+, and [Cr(NH3)6] 2+
11. Show how aniline can be converted to 4-bromoiodobenzene. (Mention all the steps involved.)
OR
(a) Write the IUPAC name and structure of the product obtained by the reaction of ethanamine and benzoyl chloride.
(b) Can the product obtained in (a) undergo the Hoffmann degradation reaction? If yes, write the structure of the product that will be formed. If no, explain why.
SECTION C
A major goal for the food scientist is the prediction of the change in the quality of a particular food as a function of both time and environmental conditions. This has become the focus of many research and development projects because the information obtained is needed by those in the food industry so that they can set an open date for the food on the package (e.g., a “use by” or “best if used by” date) so that consumers are better informed in handling the product. In order to make useful predictions about shelf life, the research scientist needs information regarding the kinetics of the reactions leading to loss of quality or nutritional value as a function of the reaction phase conditions in the food and the external environment. Some general modes of food deterioration are:
(1) Microbial decay of food: The initial population load and endpoint in terms of toxin level or the maximum allowed organism numbers are needed to make predictions of the change in the concentration level of the microbe with time. Much literature data exist for the growth rate constants of microbes under certain conditions. To keep this mode of food deterioration in mind, the food corporation of India (FCI) mandates that the concentration of a microbial in any particular canned food would be unacceptable with a maximum +30% change from the initial value of a microbial.
(2) Senescence: Once a plant is harvested or an animal slaughtered the tissues are deprived of any external source of carbon or nitrogen, and thus utilize their internal carbohydrate, protein, or fat as a source of energy. They do this by continuing their normal enzymatic reactions in an aging process usually termed senescence. Eventually, the energy sources run out, or end products accumulate to render the food unacceptable. A familiar illustration of this process is the loss of sweetness in corn on the cob during storage. The study of the rates of these senescence reactions is important to the processor who wishes to ensure high-quality ingredients in processed food. It is also important for the fresh produce supplier
(3) Enzymatic Chemical Deterioration: When a food is processed in some way (heated, salted, dried, frozen, etc.) its internal structures are disrupted so that membranes are damaged. Thus, the neatly compartmentalized system is destroyed, and chemicals normally separated can now come into contact and react. These reactions then become the major modes for loss in quality. As noted above, many of the chemical reactions that cause loss of quality also lead to physical changes, such as decreased solubility (NEB, oxidation) or mushiness (enzymatic reaction, senescence). Thus, a physical property can be used as a quality index and its change over time can be treated kinetically. Other physical reactions are almost all-or-none phenomena (thawing of ice or melting of fat), or they increase in rate as temperature decreases rather than as it increases, a situation that is not treatable by most simple kinetics models. An example of the first is the sudden loss of crispness of dry snack or cereal foods when they gain moisture and reach a certain water activity. The second type is represented by loss of quality in some frozen foods due to concentration acceleration and membrane damage as temperature decreases and by the physical staling of bread, which becomes tougher faster when it is stored refrigerated as compared to room temperature.
(Source: Application of Chemical Kinetics to Deterioration of Foods 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 1st June 2021, what should be the expiry date of this food as per the mandate of FCI? (given the average rate constant of microbial decay is 2 units day-1)
(ii) The archaeological department uses kinetics theory to find the age of plants/trees. The department found an artifact of a rare tree having only 80% of the 14C found in the living tree. Find the age of the sample if t1/2 of the 14C is 5730 years.
(iii) Through the help of a graph, show the variation in the amount of quality index(factor) of food vs time for zero and 1st order reaction.
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