Chemistry 9701/22 — October/November 2010

Cambridge AS Level · AS Level Structured Questions · worked solutions for every part, with the mark scheme

questions

marks

minutes

Topics Atoms, Molecules and Stoichiometry · Introduction to Organic Chemistry · Group 17 · Nitrogen and Sulfur · Equilibria · Reaction Kinetics · +4 more

Q1Atoms, Molecules and StoichiometryFree sample

In 1814, Sir Humphrey Davy and Michael Faraday collected samples of a flammable gas, A, from the ground near Florence in Italy.

They analysed A which they found to be a hydrocarbon. Further experiments were then carried out to determine the molecular formula of A.

(a)

What is meant by the term molecular formula?

(b)

Davy and Faraday deduced the formula of A by exploding it with an excess of oxygen and analysing the products of combustion.

Complete and balance the following equation for the complete combustion of a hydrocarbon with the formula $\text{C}_x\text{H}_y$ .

\text{C}_x\text{H}_y + \left(x + \frac{y}{4}\right)\text{O}_2 \rightarrow \dots\dots\dots\dots\dots\dots\dots\dots\dots\dots\dots\dots\dots\dots + \dots\dots\dots\dots\dots\dots\dots\dots\dots\dots\dots\dots\dots\dots

(c)

When $10\text{ cm}^3$ of A was mixed at room temperature with $50\text{ cm}^3$ of oxygen (an excess) and exploded, $40\text{ cm}^3$ of gas remained after cooling the apparatus to room temperature and pressure.

When this $40\text{ cm}^3$ of gas was shaken with an excess of aqueous potassium hydroxide, $\text{KOH}$ , $30\text{ cm}^3$ of gas still remained.

(i)

What is the identity of the $30\text{ cm}^3$ of gas that remained at the end of the experiment?

(ii)

The combustion of A produced a gas that reacted with the $\text{KOH(aq)}$ .

What is the identity of this gas?

(iii)

What volume of the gas you have identified in (ii) was produced by the combustion of A?

$\dots\dots\dots\dots\dots\dots\dots\dots\dots\dots\dots\dots\dots\dots\text{cm}^3$

(iv)

What volume of oxygen was used up in the combustion of A?

$\dots\dots\dots\dots\dots\dots\dots\dots\dots\dots\dots\dots\dots\dots\text{cm}^3$

(d)

Use your equation in (b) and your results from (c)(iii) and (c)(iv) to calculate the molecular formula of A.

Show all of your working.

The rest of this paper

4 more questions

Q2Nitrogen and Sulfur · Equilibria · Reaction Kinetics14M
Q3Introduction to Organic Chemistry · Hydrocarbons · Atoms, Molecules and Stoichiometry · Chemical Bonding · Chemical Energetics18M
Q4Halogen Compounds · Group 17 · Introduction to Organic Chemistry14M
Q5Group 173M

Loading the full paper…