S1.4 Counting particles by mass: The mole Questionbank

Practice S1.4 Counting particles by mass: The mole with authentic IB Chemistry exam questions for both SL and HL students. This question bank mirrors Paper 1A, 1B, 2 structure, covering key topics like atomic structure, chemical reactions, and organic chemistry. Get instant solutions, detailed explanations, and build exam confidence with questions in the style of IB examiners.

Paper

Level

Question 1

SLPaper 2

A marine biologist studies the effect of ocean acidification on calcium carbonate shells. In the lab, she reacts powdered ${CaCO_3}$ with excess hydrochloric acid and collects the carbon dioxide gas evolved. The reaction is:

$CaCO_3(s)+2HCl(aq)\to CaCl_2(aq)+H_2O(l)+CO_2(g)$

She starts with a $1.25\ \mathrm{g}$ sample of ${CaCO_3}$ and the gas collected has a volume of $240\ \mathrm{cm^3}$ at room temperature and pressure (RTP, $24\ \mathrm{dm^3\ mol^{-1}}$ for gas molar volume).

Calculate the number of moles of ${CaCO_3}$ in the sample.

[2]

Calculate the theoretical volume of ${CO_2}$ that should be produced at RTP.

[1]

Determine the percentage yield of the reaction based on the volume of gas collected.

[2]

Calculate the number of ${CO_2}$ molecules collected using Avogadro’s constant.

[2]

State one possible reason why the percentage yield is less than 100%.

[1]

Suggest one method the student could use to improve the accuracy of the experiment.

[1]

Question 2

SLPaper 2

A student is studying the amount of substance in chemical samples.

Define the term mole.

[1]

Calculate the number of moles in $18.0\ \mathrm{g}$ of water.

[1]

State the number of water molecules in this sample.

[1]

Question 3

SLPaper 2

Calcium carbonate is commonly used as an antacid. A tablet contains $5.00\ \mathrm{g}$ of calcium carbonate.

Write the chemical formula of calcium carbonate.

[1]

Calculate the molar mass of calcium carbonate.

[1]

Calculate the amount in moles of calcium carbonate in the tablet.

[1]

State the number of calcium ions present in this amount.

[1]

Question 4

SLPaper 2

A student investigates the decomposition of hydrated copper(II) sulfate by heating a blue crystalline sample in a crucible.

$CuSO_4\cdot5H_2O(s)\to CuSO_4(s)+5H_2O(g)$

The initial mass of hydrated copper(II) sulfate was $6.25\ \mathrm{g}$ and after heating, the mass of the remaining anhydrous solid was $3.98\ \mathrm{g}$ .

Calculate the molar mass of $CuSO_4\cdot5H_2O$ .

[1]

Determine the mass of water lost during heating.

[1]

Calculate the number of moles of water lost.

[1]

Calculate the number of moles of $CuSO_4\cdot5H_2O$ originally present.

[1]

Using your answers, verify the empirical ratio of water to salt and comment on its consistency with the formula.

[2]

Question 5

SLPaper 1A

How many moles is 2.0 g of sodium hydroxide?

Question 6

SLPaper 1A

Which amount, in mol, of potassium chloride is needed to make 250 $cm^3$ of 0.10 $mol \, dm^{−3}$ solution?

Question 7

SLPaper 1A

Which sample contains the fewest moles of HCl?

$N_A = 6.02 × 10^{23} \ mol^{–1}.$

Molar volume of an ideal gas at $STP = 22.7 \ dm^3 \ mol^{–1}$ .

Question 8

SLPaper 1A

5.0 $\mathrm{cm}^3$ of 2.00 $\mathrm{mol \, dm}^{-3}$ sodium carbonate solution, $Na_2CO_3$ (aq), was added to a volumetric flask and the volume was made up to 500 $\mathrm{cm}^3$ with water.

What is the concentration, in $\mathrm{mol \, dm}^{-3}$ , of the solution?

Question 9

SLPaper 1A

How many moles of $\mathrm{CuS}_{2}$ are required to produce 32 g of $\mathrm{SO}_{2}$ ?

$4 \mathrm{CuS}_{2}(\mathrm{s})+11 \mathrm{O}_{2}(\mathrm{g}) \rightarrow 2 \mathrm{Cu}_{2} \mathrm{O}_{3}(\mathrm{s})+8 \mathrm{SO}_{2}(\mathrm{g})$

Question 10

HLPaper 1A

What is the volume, in $cm^3$ , of the final solution if $100 \, cm^3$ of a solution containing 1.42 g of sodium sulfate, $Na_2SO_4$ , is diluted to the concentration of $0.020 \, mol \, dm^{-3}$ ?