CAIE IGCSE Chemistry 3.1 Formulae Questions

Covered syllabus points

3.1.1—Formulae of the elements and compounds 3.1.2—Molecular formula of a compound as the 3.1.3—Deduce the formula of a simple 3.1.4—Construct word equations and symbol 3.1.5—Empirical formula of a compound as the 3.1.6—Deduce the formula of an ionic 3.1.7—Construct symbol equations with state 3.1.8—Deduce the symbol equation with state

[Maximum number: 1]

Caffeine is a stimulant found in coffee.

caffeine

Which formula represents caffeine?

$\mathrm{C}_{7} \mathrm{H}_{10} \mathrm{~N}_{4} \mathrm{O}_{2}$

$\mathrm{C}_{8} \mathrm{H}_{10} \mathrm{~N}_{3} \mathrm{O}_{2}$

$\mathrm{C}_{8} \mathrm{H}_{10} \mathrm{~N}_{4} \mathrm{O}_{2}$

$\mathrm{C}_{8} \mathrm{H}_{11} \mathrm{~N}_{4} \mathrm{O}_{2}$

[Maximum number: 1]

Caffeine is a stimulant found in coffee.

Figure for Question 2 — CAIE IGCSE Chemistry

caffeine

Which formula represents caffeine?

$\mathrm{C}_{7} \mathrm{H}_{10} \mathrm{~N}_{4} \mathrm{O}_{2}$

$\mathrm{C}_{8} \mathrm{H}_{10} \mathrm{~N}_{3} \mathrm{O}_{2}$

$\mathrm{C}_{8} \mathrm{H}_{10} \mathrm{~N}_{4} \mathrm{O}_{2}$

$\mathrm{C}_{8} \mathrm{H}_{11} \mathrm{~N}_{4} \mathrm{O}_{2}$

[Maximum number: 2]

Sulfur is a Group VI element.

(a)

An acid containing sulfur reacts with sodium hydroxide, NaOH , to form a salt and water. The salt has the formula $\mathrm{Na}_{2} \mathrm{SO}_{3}$ .

[ 2 ]

(i)

Deduce the formula of this acid.

[ 1 ]

$\mathrm{H}_{2} \mathrm{SO}_{3}$

(ii)

Deduce the formula of the anion in $\mathrm{Na}_{2} \mathrm{SO}_{3}$ .

[ 1 ]

$\mathrm{SO}_{3}{ }^{2-}$

[Maximum number: 1]

Sulfur is a Group VI element.

An acid containing sulfur reacts with sodium hydroxide, NaOH , to form a salt and water. The salt has the formula $\mathrm{Na}_{2} \mathrm{SO}_{3}$ .

Deduce the formula of this acid.

$\mathrm{H}_{2} \mathrm{SO}_{3}$

[Maximum number: 2]

This question is about the elements sodium and fluorine and the compound sodium fluoride.

Sodium reacts with fluorine to form sodium fluoride.

Write a symbol equation for this reaction.

$2 \mathrm{Na}+\mathrm{F}_{2} \rightarrow 2 \mathrm{NaF}$

M1 NaF(1)

Has to be the only product

M2 equation completely correct(1)

[Maximum number: 1]

What is the empirical formula of ethanoic acid?

CHO

$\mathrm{CH}_{2} \mathrm{O}$

$\mathrm{C}_{2} \mathrm{H}_{2} \mathrm{O}$

$\mathrm{C}_{2} \mathrm{H}_{4} \mathrm{O}_{2}$

[Maximum number: 1]

This question is about metals.

Zinc oxide neutralises both acids and bases.

When zinc oxide neutralises aqueous sodium hydroxide, sodium zincate is formed.

The formula of the zincate ion is $\mathrm{ZnO}_{2}{ }^{2-}$ .
Deduce the formula of sodium zincate.

$\mathrm{Na}_{2} \mathrm{ZnO}_{2}$

[Maximum number: 3]

Lead(II) bromide, $\mathrm{PbBr}_{2}$ , is an insoluble salt and is made by precipitation.

Write an ionic equation for the precipitation reaction which produces lead(II) bromide. Include state symbols.

$\mathrm{Pb}^{2+}(\mathrm{aq})+2 \mathrm{Br}(\mathrm{aq}) \rightarrow \mathrm{PbBr}_{2}(\mathrm{~s})$

M1 $\mathrm{PbBr}_{2}$ as the only product (1)

M2 $\mathrm{Pb}^{2+}+2 \mathrm{Br}$ as the only reactants in a balanced equation(1)

M3 state symbols
$(a q)+(a q) \rightarrow(s)(1)$

[Maximum number: 1]

Copper(II) nitrate and zinc carbonate are heated strongly in separate test-tubes.
Which row identifies the gases produced?

copper(II) nitrate

zinc carbonate

oxygen and nitrogen dioxide

carbon dioxide only

oxygen and nitrogen dioxide

carbon dioxide and oxygen

nitrogen dioxide only

carbon dioxide and oxygen

nitrogen dioxide only

carbon dioxide only

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CAIE IGCSE Chemistry 3.1 Formulae Topic Practice

Covered syllabus points

Question 1

Question 2

Question 3

Question (a)

Question (i)

Question (ii)

Question 4

Question 5

Question 6

Question 7

Question 8

Question 9