Calculating Mass of Substances Practice Questions

Question 1

3 marks

This question is about sodium carbonate ( $\mathrm{Na_2CO_3}$ ).

Relative atomic masses ( $A_r$ ): C = 12 O = 16 Na = 23

(a)

Calculate the relative formula mass ( $M_r$ ) of sodium carbonate ( $\mathrm{Na_2CO_3}$ ).

$M_r$ = ......................................

/ 1

(b)

Calculate the number of moles of sodium carbonate in 31.8 g of $\mathrm{Na_2CO_3}$ .

Moles = ...................................... mol

/ 2

Question 2

3 marks

A student dissolved 12 g of potassium nitrate in water.

The student then added more water until the total volume of the solution was 500 cm $^3$ .

(a)

Convert 500 cm $^3$ into dm $^3$ .

Volume = ...................................... dm $^3$

/ 1

(b)

Calculate the concentration of the potassium nitrate solution in g/dm $^3$ .

Concentration = ...................................... g/dm $^3$

/ 2

Question 0

5 marks

This question is about amounts of substances.

The Avogadro constant = $6.02 \times 10^{23}$ per mole

(a)

Calculate the number of molecules in 0.25 mol of ammonia ( $\mathrm{NH_3}$ ).

Give your answer in standard form.

Number of molecules = ......................................

/ 2

(b)

Calculate the total number of atoms in 0.25 mol of ammonia ( $\mathrm{NH_3}$ ).

Number of atoms = ......................................

/ 1

(c)

A student says:

"1 mole of chlorine gas ( $\mathrm{Cl_2}$ ) contains the same number of atoms as 1 mole of neon (Ne)."

Is the student correct?

Explain your answer.

/ 2

Question 0

4 marks

Zinc carbonate decomposes when it is heated.

The equation for the reaction is:

$\mathrm{ZnCO_3} \rightarrow \mathrm{ZnO} + \mathrm{CO_2}$

Relative atomic masses ( $A_r$ ): C = 12 O = 16 Zn = 65

(a)

Give the number of moles of carbon dioxide produced when 3 moles of zinc carbonate decompose completely.

Moles of carbon dioxide = ...................................... mol

/ 1

(b)

Calculate the mass of zinc oxide produced when 25 g of zinc carbonate decomposes completely.

Mass of zinc oxide = ...................................... g

/ 3

Question 0

5 marks

Titanium is extracted by heating titanium chloride with sodium.

The equation for the reaction is:

$\mathrm{TiCl_4} + 4\mathrm{Na} \rightarrow \mathrm{Ti} + 4\mathrm{NaCl}$

Relative atomic masses ( $A_r$ ): Na = 23 Cl = 35.5 Ti = 48

(a)

Calculate the relative formula mass ( $M_r$ ) of titanium chloride ( $\mathrm{TiCl_4}$ ).

$M_r$ = ......................................

/ 1

(b)

Calculate the mass of sodium needed to produce 120 g of titanium.

Mass of sodium = ...................................... g

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Question 0

6 marks

Ammonia is made in the Haber process.

The equation for the reaction is:

$\mathrm{N_2} + 3\mathrm{H_2} \rightarrow 2\mathrm{NH_3}$

In a laboratory demonstration, 28 g of nitrogen and 3.0 g of hydrogen were mixed and allowed to react.

Relative formula masses ( $M_r$ ): $\mathrm{H_2}$ = 2 $\mathrm{N_2}$ = 28 $\mathrm{NH_3}$ = 17

(a)

What is meant by the limiting reactant?

/ 1

(b)

Show that hydrogen is the limiting reactant.

/ 3

(c)

Calculate the maximum mass of ammonia that could be produced from this mixture.

Mass of ammonia = ...................................... g

/ 2

Question 0

6 marks

A technician prepared two solutions of sodium chloride.

Table 1

Solution	Mass of sodium chloride in g	Volume of solution in cm $^3$	Concentration in g/dm $^3$
A	6.0	400	?
B	?	250	20

(a)

Calculate the concentration of solution A in g/dm $^3$ .

Concentration = ...................................... g/dm $^3$

/ 2

(b)

Calculate the mass of sodium chloride dissolved in solution B.

Mass = ...................................... g

/ 2

(c)

The technician added 100 cm $^3$ of water to solution A.

Explain the effect this has on the concentration of solution A.

/ 2

Question 0

6 marks

A student heated a sample of tin in a crucible until all of the tin had reacted with oxygen from the air to form tin oxide.

The student's results are shown in Table 2.

Table 2

	Mass in g
Crucible	24.60
Crucible and tin before heating	36.50
Crucible and tin oxide after heating	39.70

Relative atomic masses ( $A_r$ ): O = 16 Sn = 119

(a)

Calculate the mass of tin used and the mass of oxygen that reacted with it.

Mass of tin = ...................................... g

Mass of oxygen = ...................................... g

/ 2

(b)

Determine the balanced equation for the reaction between tin and oxygen.

You must show your working, including the simplest whole number ratio of moles of tin atoms to moles of oxygen atoms.

Equation ......................................

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Question 0

6 marks

A student added 6.5 g of zinc to 50 cm $^3$ of hydrochloric acid of concentration 73 g/dm $^3$ .

The equation for the reaction is:

$\mathrm{Zn} + 2\mathrm{HCl} \rightarrow \mathrm{ZnCl_2} + \mathrm{H_2}$

Relative atomic mass ( $A_r$ ): Zn = 65

Relative formula masses ( $M_r$ ): HCl = 36.5 $\mathrm{H_2}$ = 2

(a)

Show that hydrochloric acid is the limiting reactant.

/ 4

(b)

Calculate the mass of hydrogen produced in this reaction.

Mass of hydrogen = ...................................... g

/ 2

Question 0

7 marks

Sodium hydrogencarbonate is used as a raising agent in baking. It decomposes when heated.

The equation for the reaction is:

$2\mathrm{NaHCO_3} \rightarrow \mathrm{Na_2CO_3} + \mathrm{H_2O} + \mathrm{CO_2}$

Relative atomic masses ( $A_r$ ): H = 1 C = 12 O = 16 Na = 23

The Avogadro constant = $6.02 \times 10^{23}$ per mole

(a)

A factory needs to produce 2.2 kg of carbon dioxide by this reaction.

Calculate the mass of sodium hydrogencarbonate needed.

Give your answer in kg.

Mass of sodium hydrogencarbonate = ...................................... kg

/ 5

(b)

Calculate the number of carbon dioxide molecules in 2.2 kg of carbon dioxide.

Give your answer in standard form.

Number of molecules = ......................................

/ 2

Atomic Structure & the Periodic Table

Bonds, Structure & Properties of Matter

Quantitative Chemistry

Chemical Changes

Energy Changes

Chemical Change: Rate & Extent

Organic Chemistry

Chemical Analysis

Chemistry of the Atmosphere

Using Resources

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