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ISC Chemistry 2025 Competency Focused Questions (CFQ) with Answers

All 97 questions of the ISC Chemistry 2025 Competency Focused Questions (CFQ), in printed order, in full. Tap "Show answer" under a question to see its answer.

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Q11 mark · MCQOpen: Which of the following reactions will NOT form an ether through Williamson's…
Which of the following reactions will NOT form an ether through Williamson's synthesis? I: $\text{C}_2\text{H}_5\text{ONa} + \text{CH}_3\text{Br} \rightarrow$ II: $\text{C}_6\text{H}_5\text{Cl} + \text{C}_2\text{H}_5\text{ONa} \rightarrow$ III: $\text{C}_6\text{H}_5\text{ONa} + \text{CH}_3\text{I} \rightarrow$ IV: $\text{C}_2\text{H}_5\text{ONa} + (\text{CH}_3)_3\text{C—Br} \rightarrow$
  • (a)I and III
  • (b)II and III
  • (c)III and IV
  • (d)II and IV

No answer yet.

Q71 mark · MCQOpen: Depression in freezing point is a colligative property. At the same…
Depression in freezing point is a colligative property. At the same concentration in aqueous solution, select the solution that will show the largest freezing point depression.
  • (a)$\text{Na}_3\text{PO}_4$
  • (b)$\text{C}_{12}\text{H}_{22}\text{O}_{11}$
  • (c)$\text{NaCl}$
  • (d)$\text{K}_2\text{SO}_4$

No answer yet.

Q101 mark · MCQOpen: For a reaction , when a student X doubled the concentration of ‘A’, the rate of…
For a reaction $\text{A} \rightarrow \text{B} + \text{C}$, when a student X doubled the concentration of ‘A’, the rate of reaction was found to increase by eight times. The unit of rate constant ($k$) will be:
  • (a)$\text{s}^{-1}$
  • (b)$\text{mol}^{-1}\text{L s}^{-1}$
  • (c)$\text{mol}^{-2}\text{L}^2\text{s}^{-1}$
  • (d)$\text{mol L}^{-1}\text{s}^{-1}$

No answer yet.

Q141 mark · MCQOpen: The reaction of the compound A with gives an aromatic amine B. This amine on…
The reaction of the compound A with $\text{NH}_3$ gives an aromatic amine B. This amine on treatment with nitrous acid forms a diazonium salt which is used in the preparation of A. Identify A and B.
  • (a)$\text{C}_6\text{H}_5\text{NH}_2$ and $\text{C}_6\text{H}_5\text{Cl}$
  • (b)$\text{C}_6\text{H}_5\text{Cl}$ and $\text{C}_6\text{H}_5\text{OH}$
  • (c)$\text{C}_6\text{H}_5\text{CN}$ and $\text{C}_6\text{H}_5\text{Cl}$
  • (d)$\text{C}_6\text{H}_5\text{Cl}$ and $\text{C}_6\text{H}_5\text{NH}_2$

No answer yet.

Q151 mark · MCQOpen: Rahul wants to prepare chloroform in the laboratory using ethanol. The correct…
Rahul wants to prepare chloroform in the laboratory using ethanol. The correct order of preparation is:
  • (a)oxidation, liberation of $\text{Cl}_2$, hydrolysis and chlorination.
  • (b)liberation of $\text{Cl}_2$, oxidation, chlorination, hydrolysis.
  • (c)hydrolysis, oxidation, chlorination, liberation of chlorine.
  • (d)chlorination, hydrolysis, oxidation, liberation of chlorine.

No answer yet.

Q181 mark · MCQOpen: The above graph indicates the variation of molar conductivity of different…
The above graph indicates the variation of molar conductivity of different electrolytes. $\text{NaCl}$, $\text{CH}_3\text{COOH}$, $\text{KCl}$ represented as I, II, and III respectively. The order of increase in molar conductivity with concentration is:
  • (a)(II), (III), (I)
  • (b)(I), (III), (II)
  • (c)(III), (II), (I)
  • (d)(III), (I), (II)
Figure for this question

No answer yet.

Q191 mark · MCQOpen: On adding silver nitrate solution to , 1 mole of light-yellow precipitate of…
On adding silver nitrate solution to $\text{CoBr}_2\text{Cl}\cdot 4\text{NH}_3$, 1 mole of light-yellow precipitate of compound X is obtained. Which of the following statement explains this?
  • (a)2 bromine atoms are linked by primary valency.
  • (b)2 bromine atoms are linked by secondary valency.
  • (c)1 bromine atom is linked by primary valency.
  • (d)1 chlorine atom is linked by primary valency.

No answer yet.

Q201 mark · MCQOpen: Gia applied magnetic field around and , she found that is strongly attracted…
Gia applied magnetic field around $[\text{Fe}(\text{H}_2\text{O})_6]^{2+}$ and $[\text{Fe}(\text{CN})_6]^{4-}$, she found that $[\text{Fe}(\text{H}_2\text{O})_6]^{2+}$ is strongly attracted towards magnet. Which of the following explains this correctly? (P) $\text{CN}^-$ is a weak ligand. (Q) $\text{H}_2\text{O}$ is a weak ligand. (R) $[\text{Fe}(\text{H}_2\text{O})_6]^{2+}$ is inner orbital complex. (S) $[\text{Fe}(\text{CN})_6]^{4-}$ is low spin complex.
  • (a)Only (S)
  • (b)Both (P) and (Q)
  • (c)Only (R)
  • (d)Both (Q) and (S)

No answer yet.

Q241 mark · Assertion-reasonOpen: Electrophilic substitution reactions in haloarenes takes place in ortho and…

Assertion: Electrophilic substitution reactions in haloarenes takes place in ortho and para positions and the major product is para substituted haloarenes.

Reason: The halogen in the ring is not ortho and para directing, and the yield is more of para because of resonance stabilisation.

  • (a)Both Assertion (A) and Reason (R) are correct, and Reason (R) is the correct explanation of the Assertion (A).
  • (b)Both Assertion (A) and Reason (R) are correct, and Reason (R) is not the correct explanation of the Assertion (A).
  • (c)Assertion (A) is true, but Reason (R) is false.
  • (d)Assertion (A) is false, but Reason (R) is true.

No answer yet.

Q251 mark · Assertion-reasonOpen: Benzaldehyde on nitration gives Ortho and para nitro benzaldehyde.

Assertion: Benzaldehyde on nitration gives Ortho and para nitro benzaldehyde.

Reason: -CHO group in benzaldehyde shows –I effect and benzene ring shows +R effect.

  • (a)Both Assertion (A) and Reason (R) are correct, and Reason (R) is the correct explanation of Assertion (A).
  • (b)Both Assertion (A) and reason (R) are correct, but Reason (R) is not the correct explanation of Assertion (A).
  • (c)Assertion (A) is true, but Reason (R) is false.
  • (d)Assertion (A) is false, but Reason (R) is true.

No answer yet.

Q261 mark · Assertion-reasonOpen: The half-life of a first order reaction does not depend on initial…

Assertion: The half-life of a first order reaction does not depend on initial concentration of the reactant.

Reason: The initial reaction expression is present in the expression for rate constant.

  • (a)Both Assertion (A) and Reason (R) are correct, and Reason (R) is the correct explanation of Assertion (A).
  • (b)Both Assertion(A) and Reason (R) are correct, but Reason (R) is not the correct explanation of Assertion (A).
  • (c)Assertion (A) is true, but Reason (R) is false.
  • (d)Assertion (A) is false, but Reason (R) is true.

No answer yet.

Q271 mark · Assertion-reasonOpen: Ethanol is less acidic than water.

Assertion: Ethanol is less acidic than water.

Reason: The electron releasing inductive effect of the ethyl group decreases the acidic character.

  • (a)Both Assertion (A) and Reason (R) are correct, and Reason (R) is the correct explanation of Assertion (A).
  • (b)Both Assertion (A) and Reason (R) are correct, but Reason (R) is not the correct explanation of Assertion (A).
  • (c)Assertion (A) is true, but Reason (R) is false.
  • (d)Assertion (A) is false, but Reason (R) is true.

No answer yet.

Q281 mark · Assertion-reasonOpen: Nucleic acids are present in all living cells.

Assertion: Nucleic acids are present in all living cells.

Reason: They are not responsible for passing the genetic information from the parent cell to the new cell.

  • (a)Both Assertion (A) and Reason (R) are correct, and Reason (R) is the correct explanation of Assertion (A).
  • (b)Both Assertion (A) and Reason (R) are correct, but Reason (R) is not the correct explanation of Assertion (A).
  • (c)Assertion (A) is true, but Reason (R) is false.
  • (d)Assertion (A) is false, but Reason (R) is true.

No answer yet.

Q432 marks · Short answerOpen: A student has carried out a suitable test to differentiate between: (a) ethyl…
A student has carried out a suitable test to differentiate between: (a) ethyl amine and diethyl amine (b) ethanol and ethyl amine. What could that chemical test be to differentiate the pairs in (a) and (b)?
(a)
Differentiate between ethyl amine and diethyl amine.
(b)
Differentiate between ethanol and ethyl amine.

No answer yet.

Q492 marks · Short answerOpen: Rohan arranged three coulometers in series and passed one faraday of charge for…
Rohan arranged three coulometers in series and passed one faraday of charge for a definite time to all three electrolytes as shown in the picture given below:
Figure for this question
(a)
What will be ratio of number of moles of positive ions liberated at cathode in each coulometer?
(b)
If he passed 4825 coulombs of charge through the electrolytes, how many gram-equivalent of copper will be deposited at the cathode?

No answer yet.

Q502 marks · Short answerOpen: Yash measures the conductivity of two different solutions of 1M Ethanoic acid…
Yash measures the conductivity of two different solutions of 1M Ethanoic acid and 1M HCl each at $25^\circ\text{C}$.
(a)
Will he observe the same conductivity value for both the solutions? Justify your answer.
(b)
What will be the effect on conductivities when he keeps on diluting the solutions? Explain with the help of a graph.

No answer yet.

Q512 marks · Short answerOpen: The standard reduction potentials of the following electrodes are given below…
The standard reduction potentials of the following electrodes are given below. Answer the questions that follow:
ElectrodesSRP values
$\text{Fe}^{2+}/\text{Fe}$-0.44V
$\text{Mg}^{2+}/\text{Mg}$-2.37V
$\text{I}_2/2\text{I}^-$+0.54V
$\text{Ag}^+/\text{Ag}$+0.88V
(a)
Which substance/s could be used to convert iodide ions to iodine?
(b)
From the given reactions which reaction is spontaneous and why? I: $\text{Fe}^{2+} + 2\text{Ag} \rightarrow 2\text{Ag}^{+1} + \text{Fe}$ II: $\text{Fe}^{2+} + \text{Mg} \rightarrow \text{Mg}^{2+} + \text{Fe}$

No answer yet.

Q562 marks · Short answerOpen: Write equation for the following observations: Potassium permanganate on…
Write equation for the following observations:
(a)
Potassium permanganate on reaction with potassium iodide in acidic medium releases iodine gas, water and the sulphates of potassium and manganese. Give the balanced equation for the reaction.
(b)
Potassium permanganate on reaction with oxalic acid in acidic medium gives salts of Potassium and Manganese along with water molecules and carbon dioxide gas. Give the complete and balanced equation.

No answer yet.

Q653 marks · Short answerOpen: Mention True or False and correct the wrong statements. The observed order of…
Mention True or False and correct the wrong statements.
(a)
The observed order of basic strength of amines is: $\text{NH}_3 > (\text{C}_2\text{H}_5)_2\text{NH} > (\text{C}_2\text{H}_5)_3\text{N}$.
(b)
+I effect is maximum in $1^\circ$ amine than $3^\circ$ amine.
(c)
N,N-dimethyl aniline is a stronger base than aniline.

No answer yet.

Q663 marks · Short answerOpen: In the box certain reagents are given in the form of clues: 'dehydrating agent…
In the box certain reagents are given in the form of clues: 'dehydrating agent, alkali dissolved in alcohol, Primary amine, anaesthesia, poisonous gas, salt, universal solvent'. Identify the clue and complete the equation: $-\text{NH}_2 + \text{____} + \text{____} \rightarrow \text{____} + \text{____} + \text{____}.$

No answer yet.

Q673 marks · Short answerOpen: Answer the following: A patient was given a certain amount of iodine-131 as a…
Answer the following:
Figure for this question
(a)
A patient was given a certain amount of iodine-131 as a part of a diagnostic procedure for thyroid disorder. Given that the half-life of radioactive $^{131}\text{I}$ is 8 days, what fraction of the initial $^{131}\text{I}$ would be present in a patient after 32 days if none of it were eliminated through natural body processes?
(b)
The potential energy diagram, for a multistep reaction is given below: (i) Which step will be the rate determining step of the reaction? (ii) Which step is faster $\text{A} \rightarrow \text{B}$ or $\text{B} \rightarrow \text{C}$?

No answer yet.

Q683 marks · Short answerOpen: Answer the following questions: Aman and Rohan were working on the kinetics…
Answer the following questions:
Figure for this question
(a)
Aman and Rohan were working on the kinetics involved in decomposition of hydrogen peroxide in the presence of iodide ions. $\text{H}_2\text{O}_2(l) \rightarrow \text{H}_2\text{O} + \frac{1}{2}\text{O}_2(g)$ They both had their respective hypothesis as follows: According to Aman the rate will be affected by changing the concentrations of hydrogen peroxide and iodide ions as iodide ions are involved in the reaction. According to Rohan the rate will only be affected by changing the concentration of hydrogen peroxide. They carried out several experiments to check their respective hypothesis. Their results are shown graphically below: (i) What do you think whose hypothesis is correct and why? (ii) Do you think that the half -life of this reaction will change if concentration of hydrogen peroxide is reduced to half. Give a reason.
(b)
In a chemical reaction, two reactants take part. The rate of reaction is directly proportional to the concentration of one of them and inversely proportional to the concentration of other. What will be the unit of its rate constant if the concentration terms are in mol/L?

No answer yet.

Q703 marks · Short answerOpen: Answer the following questions: Two students took the solution of same amino…
Answer the following questions:
Figure for this question
(a)
Two students took the solution of same amino acid at different pH and applied potential difference to their solutions respectively. (i) What do you think which student will observe a potential difference zero and why? (ii) What would you do in order to get a positive observation?
(b)
The graph given below shows the rate of enzyme-catalysed reaction with temperature: (i) Why does the rate of reaction decrease at high temperature?

No answer yet.

Q723 marks · NumericalOpen: Nandini wants to electroplate her bracelet with silver. She gives the bracelet…
Nandini wants to electroplate her bracelet with silver. She gives the bracelet to an artist.
(a)
After electroplating she gets the information that 1.6117g of the metal is deposited when electric current of 0.2 ampere is passed for 2 hours. How will she make the confirmation that the metal deposited is silver by using the data?
(b)
Which law is applicable to solve the problem?

No answer yet.

Q763 marks · NumericalOpen: During a study trip, students visited a lake and took out water sample which…
During a study trip, students visited a lake and took out water sample which was rich in potassium chloride salt. They performed an experiment to calculate the boiling point of lake water which was found to be $100.025^\circ\text{C}$. If 500 g of the water sample was used for calculation ($K_b = 0.52\text{ K kg mol}^{-1}$) and there was 0.42 g KCl in the 500 ml sample, what is the observed molecular mass of KCl in the lake sample?

No answer yet.

Q773 marks · NumericalOpen: A student X was doing an experiment by taking 0.15 g acetic acid in 40 g of…
A student X was doing an experiment by taking 0.15 g acetic acid in 40 g of benzene. He suddenly observed that the freezing point of the mixture is lowered by $0.40^\circ\text{C}$. Do you think that association of acetic acid has taken place? If yes, what will be degree of association ($K_f$ of benzene = $5.12\text{ K kg mol}^{-1}$)?

No answer yet.

Q793 marks · Short answerOpen: A scientist while working in the lab accidently removed the labels from the…
A scientist while working in the lab accidently removed the labels from the carboxylic acid bottles and phenol. He had three bottles in which he had kept formic acid, acetic acid and phenol. Can you suggest a chemical test which he can perform to positively identify the acids so that he can label the bottles correctly?

No answer yet.

Q803 marks · Short answerOpen: Geet has set-up the following galvanic cell by taking the electrolyte solution…
Geet has set-up the following galvanic cell by taking the electrolyte solution of $\text{Pb}(\text{NO}_3)_2$ and $\text{CrCl}_3$. $E^\circ = -0.13\text{ V}$ $E^\circ = -0.74\text{ V}$
Figure for this question
(a)
How will you design the feasible cell by taking appropriate salt solution in place of solution A and B?
(b)
What is the applicability of the above cell?
(c)
Consider, salt bridge is filled with Potassium Chloride (KCl) solution. How does salt bridge maintain electrical neutrality?

No answer yet.

Q813 marks · Short answerOpen: Answer the following: Graphical method fails to give the value of molar…
Answer the following:
(a)
Graphical method fails to give the value of molar conductivity at infinite dilution of weak electrolyte. Explain.
(b)
To know the value of molar conductivity at infinite dilution for weak electrolyte, Kohlrausch’s law is effective. Explain.
(c)
Draw the graph to show the variation of molar conductivity of a weak electrolyte with concentration.

No answer yet.

Q823 marks · Short answerOpen: Observe the following graph for ionisation enthalpies of first, second and…
Observe the following graph for ionisation enthalpies of first, second and third transition series. Answer the following questions:
Figure for this question
(a)
Why does the ionisation energy increase across a transition series?
(b)
The ionisation energies are nearly equal for first and second transition series but abruptly increases for third transition series. Explain.
(c)
Which element would have higher density, technetium or rhenium? Justify your answer.

No answer yet.

Q833 marks · Short answerOpen: Vitamins are required in very small amount for the healthy growth of organisms…
Vitamins are required in very small amount for the healthy growth of organisms. When a person does not get a particular vitamin in diet, she/he may suffer from certain diseases. Normal functioning of an organism can be greatly affected due to deficiency of vitamins in the body.
(a)
Which vitamin deficiency causes rickets and scurvy?
(b)
Do you think, all vitamins are soluble in water? Explain by giving an example.
(c)
Explain avitaminosis.

No answer yet.

Q843 marks · Short answerOpen: The concept of Osmosis is frequently used in medical field. On the other hand…
The concept of Osmosis is frequently used in medical field. On the other hand, reverse osmosis has also found application in desalination process. Both these processes play a very useful role in the growth and development of humankind.
(a)
Explain where in medical field the concept of osmosis is used.
(b)
The place close to the sea can use reverse osmosis (RO) for desalination. Explain how that can be done.
(c)
A saturated salt solution makes a boiled peeled egg shrink. Why?

No answer yet.

Q853 marks · Short answerOpen: Chloroform was synthesised in the year 1847. It was mainly used in the medicine…
Chloroform was synthesised in the year 1847. It was mainly used in the medicine industry. When exposed to sunlight it forms a poisonous gas called phosgene. To prevent this, a small quantity of a compound which has a molecular formula $\text{C}_2\text{H}_6\text{O}$ is added.
(a)
What is the chemical formula of phosgene?
(b)
Which chemical is added to prevent the formation of phosgene.
(c)
Where is chloroform used in the field of medicine?

No answer yet.

Q873 marks · Short answerOpen: Sodium ferrocyanide is used as anti-caking agent in salts and salt substitute…
Sodium ferrocyanide is used as anti-caking agent in salts and salt substitute. Due to contact with atmospheric moisture, table salt undergoes clumping. Adding certain amount of sodium ferrocyanide can prevent this from occurring. Consider the coordination compounds $\text{Na}_4[\text{Fe}(\text{CN})_6]$ and $[\text{Fe}(\text{H}_2\text{O})_6]\text{Cl}_2$. Based on above description, answer the following questions:
(a)
Though cyanide is poisonous, potassium ferrocyanide is used as food additive. Explain.
(b)
Which compound will be more stable $\text{Na}_4[\text{Fe}(\text{CN})_6]$ or $[\text{Fe}(\text{H}_2\text{O})_6]\text{Cl}_2$? Justify your answer.
(c)
Write the hydrate isomer of $[\text{Fe}(\text{H}_2\text{O})_6]\text{Cl}_2$, which gives one mole of precipitate with $\text{AgNO}_3$ solution.

No answer yet.

Q883 marks · Short answerOpen: Food and drug administration (FDA) has approved that Ethylenediamine tetra…
Food and drug administration (FDA) has approved that Ethylenediamine tetra acetate (EDTA) is a medication in the treatment of lead poisoning. It is also used in the estimation of $\text{Ca}^{2+}$ and $\text{Mg}^{2+}$ during removal of hardness in water.
(a)
Which type of a ligand is EDTA?
(b)
Why EDTA is used in the treatment of lead poisoning?
(c)
What is the geometry of EDTA complex?

No answer yet.

Q893 marks · Short answerOpen: Alcohol and phenols are hydroxy derivatives of hydrocarbons. Both have the…
Alcohol and phenols are hydroxy derivatives of hydrocarbons. Both have the tendency to form intermolecular hydrogen bonding. Thus, they have higher boiling point and high solubility in water. As the O-H bond is polar in nature they also exhibit acidic property. Acidic characteristic depends upon inductive effect and resonance stabilization. The position and nature of substituents also affects the acidic strength.
(a)
Select from each pair as per the property mentioned in the bracket: (i) Ethanol, Methanol (most acidic) (ii) O-cresol and m-cresol (least acidic)
(b)
Correct the given statement and give a reason for your answer: 'The solubility of phenol is higher than alcohol.'
(c)
Compounds [X] and [Y] are functional isomers of each other with molecular formula $\text{C}_3\text{H}_8\text{O}$. (i) Draw the isomers. (ii) Which compound will have a lower boiling point and why?

No answer yet.

Q903 marks · Short answerOpen: Transition metals exhibit different oxidation states in their different types…
Transition metals exhibit different oxidation states in their different types of compounds. Due to incompletely filled d-orbitals the transition metal shows variable oxidation states, magnetic property, and tendency to form complexes. The most stable oxidation state is the one that maximizes the charge without breaking the stable electronic configuration. The highest oxidation states of transition elements are observed in their fluorides and oxides.
(a)
In which compound VO/ $\text{V}_2\text{O}_4$ vanadium has a stable oxidation state and why?
(b)
Manganese achieves its highest oxidation state with fluorine. Correct the statement with a valid reason.
(c)
Select the ion/s from the given ones that will show maximum and minimum response to the applied magnetic field: $\text{Zn}^{2+}, \text{Cu}^{2+}, \text{Mn}^{2+}$.

No answer yet.

Q913 marks · Short answerOpen: Nucleic acids are present in the nuclei of all living cells. DNA analysis is…
Nucleic acids are present in the nuclei of all living cells. DNA analysis is vital in crime scene situations. RNA is essential for most biological functions. In modern world the knowledge of RNA and DNA is vital for us.
(a)
Which nitrogenous bases constitute RNA and DNA?
(b)
Identify pyrimidine and purine from (a) part answer.
(c)
What are the structural differences in RNA and DNA?

No answer yet.

Q923 marks · Short answerOpen: Vapour pressure plays an important role in calculating boiling point and the…
Vapour pressure plays an important role in calculating boiling point and the freezing point of solutions. In cold countries salt is sprinkled on the road whereas while boiling egg, salt is added in water. Both these processes help the cause.
(a)
Explain relative lowering of vapour pressure.
(b)
How adding salt to water help in boiling of egg?
(c)
Why is salt sprinkled on road during winters?

No answer yet.

Q935 marks · Case basedOpen: Water pollution caused by toxic elements is one of the most important…
Water pollution caused by toxic elements is one of the most important environmental problems in the world. The objectives of this study were: the effects of chelating agents on heavy metals extraction from polluted water were carried out to examine Chelating agents like Ethylenediamine tetra acetate (EDTA), oxalic acid (OA) and citric acid (CA) were tested respectively. The effects of operating parameters, such as pH and extraction time were examined. Removal of metals was dependent on the concentration of extracting agent and raised with increasing concentration of chelating agents. Source: DOI : http://dx.doi.org/10.13005/ojc/330414
Figure for this question
(a)[1.0]
What are chelating agents?
(b)[1.0]
Name any two heavy metals which are considered toxic.
(c)[1.0]
From the above graph, arrange the order of chelating agents with respect to the % removal of toxic metals.
(d)[1.0]
Draw the structure of EDTA.
(e)[1.0]
What is the main factor on which the removal of metals depends on contaminated water using Chelating Agents?

No answer yet.

Q945 marks · Case basedOpen: Water phase change in soil causes severe damage to roads, canals, airport…
Water phase change in soil causes severe damage to roads, canals, airport runways and other buildings. The freezing point is an important indicator to judge whether the soil is frozen or not. It is found that the addition of salt can effectively reduce the frost heave of soil. The graphs given below show the change in freezing point with different concentrations of salt and water: Source: https://www.mdpi.com/2073-4441/12/8/2232 It is clear from the graphs that as water content is high, depression is less and as the salt concentration is high, depression is more.
Figure for this question
(a)[2.0]
2.1g $\text{CoCl}_3\cdot 6\text{NH}_3$ (molecular weight = 267.5) was dissolved in 100 g of water. The freezing point of the solution was $-0.584^\circ\text{C}$. Assuming 100% ionization of the complex salt having coordination number 6, what will be the formula of the complex. Given that: $K_f$ for water = $1.86\text{ K kg mol}^{-1}$.
(b)[1.5]
Which salt solution is the best for de-icing? 1% NaCl or 1% $\text{CaCl}_2$ [Atomic weight of Na= 23, Ca = 40, Cl = 35.5 a.m.u]
(c)[1.5]
Equimolal concentration of two different solutes X and Y undergoes dimerization and trimerization respectively in their respective solutions. What will be the ratio of observed lowering of vapour pressure in two cases?

No answer yet.

Q955 marks · Case basedOpen: The aldol condensation takes its name from aldol (3-hydroxybutanal) a name…
The aldol condensation takes its name from aldol (3-hydroxybutanal) a name introduced by Wurtz who first prepared the beta-hydroxy aldehyde from acetaldehyde in 1872. It is a base catalysed reaction, and the product of aldol condensation undergoes dehydration of intermediate beta-aldols or beta-ketals in presence of a dilute acid to form $\alpha, \beta$ unsaturated carbonyl compound. Source: https://www.researchgate.net/publication/229950129_The_Aldol_Condensation
(a)[2.0]
Write the mechanism of aldol condensation starting with acetaldehyde.
(b)[1.0]
Name the base used highlighting the role of the base catalyst in facilitating the reaction.
(c)[2.0]
What is crossed aldol condensation? Name the product formed when benzaldehyde undergoes crossed aldol condensation with acetaldehyde.

No answer yet.

Q965 marks · Case basedOpen: ‘In 1915, a senior lecturer in Biochemistry at the University of Manchester…
‘In 1915, a senior lecturer in Biochemistry at the University of Manchester named Dr. Chaim Weizmann invented a fermented process that converts starch into acetone and butanol by using Clostridium acetobutylicum. Acetone was the key component in the production of the smokeless gunpowder (cordite) used by the Allies in World War I. Acetone was previously made from calcium acetate imported from Germany, since Allies were in war with Germany, this was no longer possible.’ Source: https://www.weizmann.ac.il/WeizmannCompass/sections/people-behind-the-science/chaim-weizmann%E2%80%99s-acetone-patent-turns-100
(a)[2.0]
How will you prepare acetone from calcium acetate?
(b)[2.0]
If butan-2-ol is oxidised by $\text{K}_2\text{Cr}_2\text{O}_7$, which ketone will be produced? Give the balanced chemical reaction.
(c)[1.0]
How would you obtain acetone from acetyl chloride?

No answer yet.

Q975 marks · Case basedOpen: ‘Freidrich Wilhelm Georg Kohlrausch was a German physicist who studied the…
‘Freidrich Wilhelm Georg Kohlrausch was a German physicist who studied the electrical conductivity of electrolytic solutions. From 1875-1879 he performed numerous experiments with aqueous solutions of different salts, acids and other electrolytes. He concluded that each type of migrating ion has a specific conductivity, and it does not depend on the origin of the ion. In a simple way, his conclusions were applicable to strong electrolytes as well as more complex behaviour was observed for weak electrolytes.’ Source: https://doi.org/10.1002/elsa.202160008
(a)[1.0]
What did Kohlrausch mean when he said that each ion has specific conductivity which is independent of origin of ions?
(b)[2.0]
Explain the law proposed by Kohlrausch with example.
(c)[2.0]
How do you propose to calculate the molar conductivity of a weak electrolyte (acetic acid) by using his law?

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