IB Chemistry SL 1.4 The Mole

Practise converting between mass, amount and particles, deriving formulas, calculating solution concentration and applying Avogadro's law to reacting gas volumes.

Syllabus
First assessment 2025
Topic
1.4
Level
SL

Exam points

  • convert between mass, amount and specified particles using molar mass and Avogadro's constant
  • derive empirical and molecular formulas from composition or combustion measurements
  • calculate molar concentration or prepare a standard solution from mass, volume and molar mass
  • apply Avogadro's law and balanced gas-volume ratios to find products or excess reactant

Covered syllabus points

1.4.1—Mole (mol)1.4.2—Relative atomic mass (Ar) and relative formula mass (Mr)1.4.3—Molar mass (M)1.4.4—Empirical and molecular formulas1.4.5—Molar concentration1.4.6—Avogadro's law

1.4 The mole question 1

[Maximum number: 1]

How many ions are present in 0.20 mol of (NH4)2SO4\left(\mathrm{NH}_{4}\right)_{2} \mathrm{SO}_{4} ?

A

0.20×1×6×10230.20 \times 1 \times 6 \times 10^{23}

B

0.20×2×6×10230.20 \times 2 \times 6 \times 10^{23}

C

0.20×3×6×10230.20 \times 3 \times 6 \times 10^{23}

D

0.20×7×6×10230.20 \times 7 \times 6 \times 10^{23}

1.4 The mole question 2

[Maximum number: 1]

The element boron has two naturally occurring isotopes, 10 B{ }^{10} \mathrm{~B} and 11 B{ }^{11} \mathrm{~B}.

The percentage abundance of the isotopes of boron can be determined with a mass spectrometer. The diagram shows the operation of a mass spectrometer.

Figure for Question 1.4 The mole question 2 — IB Chemistry SL

Identify the species that is used as the scale for the mass of the isotopes.

1.4 The mole question 3

[Maximum number: 1]

Chlorine undergoes many reactions.

2.67 g of manganese(IV) oxide was added to 200.0 cm3200.0 \mathrm{~cm}^{3} of 2.00moldmm−3HCl2.00 \mathrm{moldm} \mathrm{m}^{-3} \mathrm{HCl}.

MnO2( s)+4HCl(aq)→Cl2( g)+2H2O(l)+MnCl2(aq)\mathrm{MnO}_{2}(\mathrm{~s})+4 \mathrm{HCl}(\mathrm{aq}) \rightarrow \mathrm{Cl}_{2}(\mathrm{~g})+2 \mathrm{H}_{2} \mathrm{O}(\mathrm{l})+\mathrm{MnCl}_{2}(\mathrm{aq})

Calculate the amount, in mol, of manganese(IV) oxide added.

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