 Chemistry CIE iGCSE:
Calculations 1b

For Double and Triple sciences

Grab a calculator and a copy of the periodic table!

(This test has only 10 questions, but may take 15 - 20 mins).

Note: "rtp" = room temperature and pressure

This test mainly covers calculations involving volumes of gases

1. In an experiment to investigate the rate of decomposition of hydrogen peroxide a student collected 240 cm3 of oxygen gas at rtp. How many moles of oxygen gas did he collect?

[Molar volume of any gas at rtp = 24 dm3]

• A.   100
• B.   10
• C.   0.010
• D.   0.1

Q2-3:
Industrially nitrogen gas reacts with hydrogen gas in the Haber process to produce 340 kg of ammonia gas.

N2(g)  +  3H2(g)  2NH3(g)

2. How many moles of ammonia formed? [Mr of NH3 = 17]
• A.   10
• B.   20
• C.   10,000
• D.   20,000
3. What volume of nitrogen gas was needed to produce this amount of ammonia at rtp?

[Molar volume of any gas =24 dm3 at rtp]

• A.   240 dm3
• B.   240,000 dm3
• C.   480 dm3
• D.   480,000 dm3

Q4-5:
200 cm3 of a 2.0 mol/dm3 solution of potassium hydroxide was used to absorb carbon dioxide gas in the following reaction:

2KOH(aq)  +  CO2(g)  K2CO3(aq)  +  H2O(l)

4. How many moles of potassium hydroxide were used and what amount, in moles, of carbon dioxide could be absorbed by this solution?

 Moles of KOH used Moles of CO2 absorbed A 0.4 0.4 B 0.4 0.2 C 400 400 D 400 200
5. What volume of carbon dioxide could be absorbed by this solution at room temperature and pressure?
[molar volume of any gas = 24 dm3 at rtp]
• A.   4.8 cm3
• B.   480 cm3
• C.   4.8 dm3
• D.   4800 dm3
6. Calculate the maximum volume of hydrogen formed at rtp when 6.5g of zinc reacts completely with excess hydrochloric acid in the following reaction:

Zn  +  2HCl  ZnCl2  +  H2

(Ar(Zn) = 65; Molar volume of any gas at rtp = 24dm3)

• A.   2.4dm3
• B.   4.8dm3
• C.   12dm3
• D.   24dm3

7. 200cm3 of hydrogen gas reacts completely with 100cm3 of oxygen gas to form water vapour:

2H2(g)  +   O2(g)  2H2O(g)

What is the maximum volume of water vapour formed?
(All volumes are measured at the same temperature and pressure).

• A.   100cm3
• B.   200cm3
• C.   300cm3
• D.   400cm3

Q8-9:
The salt copper(II)chloride was prepared by adding excess copper(II)carbonate to 0.100 mol of dilute hydrochloric acid.  The equation for the reaction is:

CuCO3(s) + 2HCl(aq)  CuCl2(aq) + H2O(l) + CO2(g)

8. Calculate the mass of copper(II)carbonate that will react with the 0.100 mol of hydrochloric acid.
[Mr of CuCO3 = 123.5]
• A.   24.70 g
• B.   18.53 g
• C.   12.35 g
• D.   6.18 g
9. Calculate the volume of carbon dioxide gas that will be formed in this reaction at rtp.
[Molar volume of any gas at rtp=24 dm3]
• A.   0.6 dm3
• B.   1.2 dm3
• C.   2.4 dm3
• D.   4.8 dm3
10. A student prepared 0.002 moles of gas and found that, under the conditions of his experiment, it occupied a volume of 40 cm3.

What was the molar volume of the gas under these conditions?

• A.   48 cm3
• B.   48 dm3
• C.   20,000 cm3
• D.   24,000 cm3