2022 A Level H2 Chemistry Paper 1 Solutions - Questions 11 to 20

Question 11

 2022 p1 11 question

Answer: D

Topic: Energetics


Enthalpy change is negative as given in the question.

From the balanced equation, there is an increase in moles of gas, increase in degree of disorder hence entropy change is positive.

When ΔH is negative and (-TΔS) term is negative, we can deduce Gibbs free energy is always negative and reaction is always feasible or spontaneous.

 2022 p1 11 explain

Question 12

 2022 p1 12 question

Answer: C

Topic: Kinetics


In experiment 2, lead(IV) oxide is added and same mass of it was recovered.

There is also an increase in rate of volume of oxygen gas collected.

This means PbO2 is a catalyst which lowers the activation energy and increase rate constant in experiment 2.

 2022 p1 12 explain

Question 13

 2022 p1 13 question

Answer: B

Topic: Chemical Equilibria


We can use the ICE table to deduce equilibrium concentrations of reactants and products.

Then substitute all these values into equilibrium constant expression to solve for Kc.

 2022 p1 13 explain

Question 14

 2022 p1 14 question

Answer: B

Topic: Buffer Solution


Use buffer equation to calculate [HCO3-]/[H2CO3] = 6266

Then inverse that ratio to find [H2CO3]/[HCO3-]

 2022 p1 14 explain

Question 15

 2022 p1 15 question

Answer: C

Topic: Solubility Product


When aqueous ammonia is added, diamminesilver complex is formed which lowers concentration of Ag+(aq).

This will shift position of equilibrium to the right, cause more AgCl salt to dissolve hence solubility will increase.

When aqueous sodium chloride is added, concentration of Cl-(aq) increases.

This will shift position of equilibrium to the left, less AgCl salt will dissolve and solubility will decrease.

 2022 p1 15 explain

Question 16

 2022 p1 16 question

Answer: C

Topic: Solubility Product


At equilibrium, silver ion concentration is 0.032 moldm-3 and sulfate ion concentration is 0.016 moldm-3.

We can then calculate Ksp to be 1.638 x 10-5 mol3dm-9.

In presence of 0.50 moldm-3 of Na2SO4, concentration of Ag+ is 2y, SO42- is approximately 0.50 since contribution of SO42- from sparingly soluble Ag2SO4 is negligible.

We can substitute these values into the same Ksp expression to solve for y and then silver ion concentration.

 2022 p1 16 explain

Question 17

 2022 p1 17 question

Answer: A

Topic: Organic Chemistry


Follow the arrow pushing to determine product and deduce which ones are carbocations.

 2022 p1 17 explain

Question 18

 2022 p1 18 question

Answer: C

Topic: Intro to Organic Chem


Optical isomers will react differently with chiral compounds with optical activity.

Since only one enantiomer has the desired activity, this means the biological receptors that react with the drug must be chiral.

Enantiomers are stereoisomers with almost identical chemical and physical properties.

Only difference in physical property is the direction of rotating plane polarised light.

 2022 p1 18 explain

Question 19

 2022 p1 19 question

Answer: B

Topic: Intro to Organic Chem


In the compound alkene is reduced to alkane and alcohol is oxidised to aldehyde.

The molecular formula for the reactant and product are the same, they are structural isomers of each other, hence the reaction can be considered isomerisation.

 2022 p1 19 explain

Question 20

 2022 p1 20 question

Answer: D

Topic: Intro to Organic Chem


On reducing all the alkenes to alkanes, we can then find the number of chiral carbons in the product.

 2022 p1 20 explain

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