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CAIE A-Level Chemistry AS 2 Atoms Molecules and Stoichiometry Questions

Practise moving between relative masses, particles, moles, formulae, equations and reacting quantities.

Syllabus
2028–2030
Course
Chemistry 9701
Level
AS

Covered syllabus points

2.1 Relative masses of atoms and molecules2.2 The mole and the Avogadro constant2.3 Formulas2.4 Reacting masses and volumes (of solutions and gases)

Question 1

[Maximum number: 3]

Copper is used in electrical equipment. It has a melting point of 1085∘C1085^{\circ} \mathrm{C}.

Question (a)

(a)

The relative isotopic masses and natural abundances of the two isotopes in a sample of copper are shown in Table 1.1.

Table 1.1

Table 1.1

[ 2 ]

Question (i)

(i)

Define the unified atomic mass unit.

[ 1 ]

Question (ii)

(ii)

Define relative atomic mass, ArA_{\mathrm{r}}, in terms of the unified atomic mass unit.

[ 1 ]

Question (b)

(b)

When KI(aq) is added to CuSO4(aq)\mathrm{CuSO}_{4}(\mathrm{aq}) the blue-coloured solution turns brown and a white precipitate of CuI(s) is seen.

The reaction between copper ions and iodide forms only two products.

[ 1 ]

Question (i)

(i)

Complete the equation for this reaction.

………..Cu2++………..I−→………..CuI+…………………………....\ldots \ldots \ldots . . \mathrm{Cu}^{2+}+\ldots \ldots \ldots . . \mathrm{I}^{-} \rightarrow \ldots \ldots \ldots . . \mathrm{CuI}+\ldots \ldots \ldots \ldots \ldots \ldots \ldots \ldots \ldots \ldots . . . .
[ 1 ]

Question 2

[Maximum number: 1]

Which of these samples of gas contains the same number of atoms as 1 g of hydrogen gas?

A

22 g of carbon dioxide ( Mr:CO2,44M_{\mathrm{r}}: \mathrm{CO}_{2}, 44 )

B

8 g of methane (Mr:CH4,16)\left(M_{\mathrm{r}}: \mathrm{CH}_{4}, 16\right)

C

20 g of neon ( Mr:Ne,20M_{\mathrm{r}}: \mathrm{Ne}, 20 )

D

8 g of ozone ( Mr:O3,48M_{\mathrm{r}}: \mathrm{O}_{3}, 48 )

Question 3

[Maximum number: 1]

Which pair of formulae is correct?

A

Ag2CO3\mathrm{Ag}_{2} \mathrm{CO}_{3} and (NH4)3NO3\left(\mathrm{NH}_{4}\right)_{3} \mathrm{NO}_{3}

B

K2HCO3\mathrm{K}_{2} \mathrm{HCO}_{3} and Zn3(PO4)2\mathrm{Zn}_{3}\left(\mathrm{PO}_{4}\right)_{2}

C

AgHCO3\mathrm{AgHCO}_{3} and K3PO4\mathrm{K}_{3} \mathrm{PO}_{4}

D

ZnCO3\mathrm{ZnCO}_{3} and (NH4)2PO4\left(\mathrm{NH}_{4}\right)_{2} \mathrm{PO}_{4}

Question 4

[Maximum number: 1]

Sample X is added to water and made up to a total volume of 200 cm3200 \mathrm{~cm}^{3}. This gives a solution of 0.100 moldm−3HCl0.100 \mathrm{~mol} \mathrm{dm}^{-3} \mathrm{HCl}.

What is X ?

A

10 cm310 \mathrm{~cm}^{3} of 1.00 moldm−3HCl1.00 \mathrm{~mol} \mathrm{dm}^{-3} \mathrm{HCl}

B

30 cm330 \mathrm{~cm}^{3} of 0.90 moldm−3HCl0.90 \mathrm{~mol} \mathrm{dm}^{-3} \mathrm{HCl}

C

50 cm350 \mathrm{~cm}^{3} of 0.40 moldm−3HCl0.40 \mathrm{~mol} \mathrm{dm}^{-3} \mathrm{HCl}

D

100 cm3100 \mathrm{~cm}^{3} of 0.30 moldm−3HCl0.30 \mathrm{~mol} \mathrm{dm}^{-3} \mathrm{HCl}

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