Measurement, Mass & Equations Practice Questions

Question 1

4 marks

This question is about magnesium and some of its compounds.

Magnesium nitrate has the formula $\mathrm{Mg(NO_3)_2}$ .

(a)

Give the number of oxygen atoms shown in one formula unit of $\mathrm{Mg(NO_3)_2}$ .

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(b)

Give the total number of atoms represented by $2\mathrm{Mg(NO_3)_2}$ .

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(c)

In a sealed flask, $4.8\ \mathrm{g}$ of magnesium reacts completely with $3.2\ \mathrm{g}$ of oxygen to produce magnesium oxide.

$2\mathrm{Mg} + \mathrm{O_2} \rightarrow 2\mathrm{MgO}$

Give the mass of magnesium oxide produced and explain your answer.

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Question 2

4 marks

Symbol equations must be balanced because no atoms are lost or made during a chemical reaction.

(a)

Balance the equation for the reaction of nitrogen with hydrogen.

$\mathrm{N_2} + \underline{\hspace{1cm}}\mathrm{H_2} \rightarrow \underline{\hspace{1cm}}\mathrm{NH_3}$

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(b)

Balance the equation for the reaction of iron with oxygen.

$\underline{\hspace{1cm}}\mathrm{Fe} + \underline{\hspace{1cm}}\mathrm{O_2} \rightarrow \underline{\hspace{1cm}}\mathrm{Fe_2O_3}$

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(c)

Calcium reacts with dilute hydrochloric acid to produce a salt and a gas.

Complete the equation for this reaction. You should balance the equation.

$\mathrm{Ca} + \underline{\hspace{1cm}}\mathrm{HCl} \rightarrow \underline{\hspace{1.5cm}} + \underline{\hspace{1.5cm}}$

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Question 3

4 marks

Table 1 shows three compounds used in medicines.

Table 1

Compound	Formula
Magnesium hydroxide	$\mathrm{Mg(OH)_2}$
Aspirin	$\mathrm{C_9H_8O_4}$
Iron(II) sulfate	$\mathrm{FeSO_4}$

Relative atomic masses ( $A_r$ ): H = 1 C = 12 O = 16 Mg = 24 S = 32 Fe = 56

(a)

Calculate the relative formula mass ( $M_r$ ) of magnesium hydroxide, $\mathrm{Mg(OH)_2}$ .

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(b)

Calculate the relative formula mass ( $M_r$ ) of aspirin, $\mathrm{C_9H_8O_4}$ .

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(c)

Give the total number of atoms shown in the formula of iron(II) sulfate, $\mathrm{FeSO_4}$ .

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Question 0

4 marks

Urea, $\mathrm{CO(NH_2)_2}$ , is used as a nitrogen fertiliser.

Relative atomic masses ( $A_r$ ): H = 1 C = 12 N = 14 O = 16

(a)

Calculate the relative formula mass ( $M_r$ ) of urea, $\mathrm{CO(NH_2)_2}$ .

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(b)

Calculate the percentage by mass of nitrogen in urea.

Give your answer to 3 significant figures.

Percentage by mass of nitrogen = .................. %

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(c)

Ammonium nitrate, $\mathrm{NH_4NO_3}$ , contains 35.0 % nitrogen by mass.

Suggest one advantage to a farmer of using urea rather than ammonium nitrate.

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Question 0

5 marks

A student heated a sample of copper in an open crucible until there was no further change in mass.

The copper reacted with oxygen in the air to produce copper oxide, CuO.

Table 2

Measurement	Mass in g
Crucible	24.10
Crucible + copper before heating	26.64
Crucible + contents after heating	27.28

(a)

Balance the equation for the reaction.

$\underline{\hspace{1cm}}\mathrm{Cu} + \mathrm{O_2} \rightarrow \underline{\hspace{1cm}}\mathrm{CuO}$

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(b)

Calculate the mass of oxygen that reacted with the copper.

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(c)

Explain, in terms of particles, why the mass of the solid in the crucible increased during the experiment.

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Question 0

6 marks

Copper carbonate decomposes when heated:

$\mathrm{CuCO_3} \rightarrow \mathrm{CuO} + \mathrm{CO_2}$

A student heated $12.35\ \mathrm{g}$ of copper carbonate in an open test tube on a balance. The mass of the test tube and its contents was recorded before and after heating.

Relative atomic masses ( $A_r$ ): C = 12 O = 16 Cu = 63.5

(a)

Show that the total relative formula mass of the products is equal to the relative formula mass of the reactant.

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(b)

Explain what happens to the mass of the test tube and its contents during the experiment.

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(c)

Suggest one change to the apparatus that would allow the student to show that mass is conserved in this reaction.

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Question 0

6 marks

A student investigated the loss in mass when $2.00\ \mathrm{g}$ of marble chips reacted with $25.0\ \mathrm{cm^3}$ of dilute hydrochloric acid in a conical flask on a balance.

The student repeated the investigation five times. The results are shown in Table 3.

Table 3

Repeat	Loss in mass in g
1	0.42
2	0.45
3	0.58
4	0.44
5	0.43

(a)

Identify the anomalous result in Table 3 and suggest one reason for this result.

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(b)

Calculate the mean loss in mass. You should ignore the anomalous result.

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(c)

Use the range of the results (ignoring the anomalous result) to estimate the uncertainty in the mean loss in mass.

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Question 0

6 marks

X is a metal that reacts with chlorine.

The equation for the reaction is:

$2\mathrm{X} + 3\mathrm{Cl_2} \rightarrow 2\mathrm{XCl_3}$

The sum of the relative formula masses ( $M_r$ ) of the products ( $2\mathrm{XCl_3}$ ) is 267.

Relative atomic mass ( $A_r$ ): Cl = 35.5

(a)

Calculate the relative atomic mass ( $A_r$ ) of X.

Relative atomic mass ( $A_r$ ) of X = ..................

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(b)

Use your answer to part (a) and the periodic table to identify metal X.

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(c)

Calculate the percentage by mass of chlorine in $\mathrm{XCl_3}$ .

Give your answer to 3 significant figures.

Percentage by mass of chlorine = .................. %

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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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Question 3

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