Formulae, Equations & Hazards Practice Questions

Question 1

3 marks

Air is a mixture of elements and compounds.

(a)

Which row shows the correct formulae of the nitrogen, oxygen and argon in the air?

	nitrogen	oxygen	argon
A	$\mathrm{N}$	$\mathrm{O}$	$\mathrm{Ar}$
B	$\mathrm{N_2}$	$\mathrm{O_2}$	$\mathrm{Ar}$
C	$\mathrm{N_2}$	$\mathrm{O_2}$	$\mathrm{Ar_2}$
D	$\mathrm{N}$	$\mathrm{O_2}$	$\mathrm{Ar}$

Put a cross ( ☒ ) in the box next to your answer.

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(b)

Inside a car engine, nitrogen and oxygen react together at high temperature to form nitrogen monoxide, $\mathrm{NO}$ .

Write the balanced equation for this reaction.

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Question 2

3 marks

Calcium hydroxide is spread on fields to neutralise acidic soil.

(a)

Which of these is the formula of calcium hydroxide?

☐ A $\mathrm{CaOH}$

☐ B $\mathrm{Ca_2OH}$

☐ C $\mathrm{Ca(OH)_2}$

☐ D $\mathrm{Ca(OH)_3}$

Put a cross ( ☒ ) in the box next to your answer.

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(b)

Calcium hydroxide also neutralises dilute nitric acid.

Complete the word equation for this reaction.

calcium hydroxide + nitric acid → ................................ + ................................

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Question 3

3 marks

Methane, $\mathrm{CH_4}$ , is the main gas in natural gas. It burns completely in oxygen to form carbon dioxide and water. The water is formed as a liquid.

Complete the balancing of the equation for this reaction and add the state symbols for each substance.

................ $\mathrm{CH_4}$ (................) + ................ $\mathrm{O_2}$ (................) → ................ $\mathrm{CO_2}$ (................) + ................ $\mathrm{H_2O}$ (................)

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Question 4

3 marks

A technician is preparing bottles of chemicals for a practical lesson. The hazard symbols on a bottle indicate the dangers associated with the contents.

(a)

Which hazard symbol should be shown on a bottle of concentrated sodium hydroxide solution?

☐ A oxidising

☐ B flammable

☐ C corrosive

☐ D hazardous to the environment

Put a cross ( ☒ ) in the box next to your answer.

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(b)

A bottle of propanone is labelled with the flammable hazard symbol.

State one safe-working precaution a student should take when using propanone in the laboratory, and give a reason for this precaution.

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Question 5

2 marks

A student adds powdered zinc carbonate to dilute sulfuric acid. The mixture fizzes.

(a)

Complete the equation for this reaction by writing the formula of the missing product.

$\mathrm{ZnCO_3 + H_2SO_4 \rightarrow\ ...............................\ + H_2O + CO_2}$

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(b)

Which row gives the correct state symbols for the zinc carbonate powder and for the dilute sulfuric acid?

	zinc carbonate	dilute sulfuric acid
A	(aq)	(l)
B	(s)	(aq)
C	(l)	(aq)
D	(s)	(l)

Put a cross ( ☒ ) in the box next to your answer.

/ 1

Question 0

4 marks

Iron is extracted in a blast furnace. Iron(III) oxide, $\mathrm{Fe_2O_3}$ , is reduced by carbon monoxide, $\mathrm{CO}$ .

(a)

In the furnace, iron(III) oxide reacts with carbon monoxide to form iron and carbon dioxide.

Write the balanced equation for this reaction.

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(b)

The carbon monoxide is made inside the furnace when carbon burns in a limited supply of oxygen.

Write the balanced equation for carbon burning in a limited supply of oxygen to form carbon monoxide.

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Question 0

3 marks

Pentane, $\mathrm{C_5H_{12}}$ , is a liquid hydrocarbon found in petrol.

Write the balanced equation for the complete combustion of pentane.

State symbols are not required.

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Question 0

3 marks

Silver nitrate solution is added to sodium chloride solution. A white precipitate of silver chloride forms.

$\mathrm{AgNO_3(aq) + NaCl(aq) \rightarrow AgCl(s) + NaNO_3(aq)}$

(a)

Write the balanced ionic equation, including state symbols, for the formation of the precipitate.

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(b)

Name the two spectator ions in this reaction.

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Question 0

4 marks

Nitric acid is manufactured from ammonia in a series of reactions.

(a)

In the first reaction, ammonia is oxidised to nitrogen monoxide over a hot catalyst.

Balance the equation for this reaction.

................ $\mathrm{NH_3}$ + ................ $\mathrm{O_2}$ → ................ $\mathrm{NO}$ + ................ $\mathrm{H_2O}$

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(b)

In the next stage, nitrogen monoxide, $\mathrm{NO}$ , reacts with oxygen to form nitrogen dioxide, $\mathrm{NO_2}$ .

Write the balanced equation for this reaction.

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Question 0

5 marks

A student neutralises dilute nitric acid with potassium hydroxide solution. The products are potassium nitrate solution and water.

(a)

Write the balanced equation for this reaction, including state symbols.

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(b)

Write the balanced ionic equation, including state symbols, for this neutralisation reaction.

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Question 0

2 marks

Many compounds are made up of a metal ion and a negative ion containing more than one element.

(a)

Chromium(III) sulfate contains $\mathrm{Cr^{3+}}$ ions and $\mathrm{SO_4^{2-}}$ ions.

Which of these is the formula of chromium(III) sulfate?

☐ A $\mathrm{CrSO_4}$

☐ B $\mathrm{Cr(SO_4)_3}$

☐ C $\mathrm{Cr_2(SO_4)_3}$

☐ D $\mathrm{Cr_3(SO_4)_2}$

Put a cross ( ☒ ) in the box next to your answer.

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(b)

A fertiliser contains ammonium ions, $\mathrm{NH_4^+}$ , and phosphate ions, $\mathrm{PO_4^{3-}}$ .

Give the formula of ammonium phosphate.

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Question 0

3 marks

A student places a piece of zinc in copper(II) sulfate solution. The blue colour of the solution fades and a brown solid forms on the zinc.

(a)

Write the word equation for this reaction.

/ 1

(b)

Write the balanced ionic equation for this reaction.

State symbols are not required.

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Question 0

4 marks

A teacher demonstrates the thermal decomposition of lead(II) nitrate, $\mathrm{Pb(NO_3)_2}$ . The solid is heated strongly in a test tube. It forms lead(II) oxide, nitrogen dioxide and oxygen. Nitrogen dioxide is a toxic brown gas.

(a)

Write the balanced equation for the thermal decomposition of lead(II) nitrate.

State symbols are not required.

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(b)

State one safe-working precaution the teacher should take during this demonstration, and give a reason for this precaution.

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Question 0

6 marks

Sodium hydroxide solution is added to iron(III) chloride solution, $\mathrm{FeCl_3(aq)}$ . A brown precipitate of iron(III) hydroxide, $\mathrm{Fe(OH)_3}$ , forms in a solution of sodium chloride.

(a)

Write the balanced equation for this reaction.

State symbols are not required.

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(b)

Write the balanced ionic equation, including state symbols, for the formation of the brown precipitate.

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Question 0

3 marks

Aluminium hydroxide, $\mathrm{Al(OH)_3}$ , is used in indigestion tablets. It reacts with dilute sulfuric acid to form aluminium sulfate and water.

Aluminium sulfate contains $\mathrm{Al^{3+}}$ ions and $\mathrm{SO_4^{2-}}$ ions.

Write the balanced equation for the reaction of aluminium hydroxide with dilute sulfuric acid.

State symbols are not required.

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Question 0

6 marks

A student is going to prepare pure, dry crystals of magnesium sulfate.

This is the student's plan.

Pour $25\ \mathrm{cm^3}$ of dilute sulfuric acid into a beaker and warm it with a Bunsen burner.
Add magnesium carbonate powder, a little at a time, until no more reacts.
Filter the mixture to remove the magnesium carbonate that has not reacted.
Heat the filtrate in an evaporating basin, as shown below, until crystals start to form, then leave it to cool.

Dilute sulfuric acid is an irritant.

Evaluate the risks in this procedure and suggest suitable precautions the student should take to reduce them.

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Key Concepts in Chemistry

States of Matter & Mixtures

Chemical Changes

Extracting Metals & Equilibria

Groups in the Periodic Table

Rates of Reaction & Energy Changes

Fuels & Earth Science

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