Chemical Quantities (AQA GCSE Combined Science: Synergy: Physical Sciences): Exam Questions

This question is about ammonium chloride.

Ammonium chloride (NH₄Cl) decomposes to produce ammonia (NH₃) and hydrogen chloride (HCl).

The reaction is reversible.

The equation for the reaction is:

NH₄Cl(s) ⇌ NH₃(g) + HCl(g)

What is the state of hydrogen chloride in this reaction?

What is the total number of atoms in the formula NH₄Cl?

Figure 7 represents the electronic structure of a chlorine atom (Cl).

Which diagram represents the electronic structure of a chloride ion (Cl⁻)?

Ammonia has the formula NH₃

Calculate the percentage (%) by mass of nitrogen (N) in NH₃

Relative atomic mass (A_r): N = 14

Relative formula mass (M_r): NH₃ = 17

Give your answer to 2 significant figures.

Figure 8 represents ammonia.

What does ‘$—$’ represent in Figure 8?

This question is about solutions.

0.4 dm³ of a solution contains 24 g of solute.

Calculate the concentration of the solution.

Use the equation:

$\text{concentration}=\frac{\text{mass of solute}}{\text{volume of solution}}$

What is meant by a ‘solute’?

Sugar solution X and sugar solution Y have different concentrations.

A student investigated which solution had the higher concentration.

The student evaporated sugar solution at a temperature of 40 °C until only sugar remained.

Figure 13 shows the equipment used.

Plan a method to show if sugar solution X or sugar solution Y has the higher concentration.

Figure 14 shows the balance.

The resolution is the smallest change in the quantity being measured that a measuring instrument can show.

What is the resolution of the balance?

Ethene (C₂H₄) is a small molecule.

Calculate the relative formula mass ($M_r$) of ethene.

Relative atomic masses ($A_r$): C = 12, H = 1

This question is about chemical quantities.

0.40 dm³ of a solution contains 48.4 g of solute.

Calculate the concentration of the solution.

Give the unit.

Calculate the number of carbon dioxide molecules in 3.00 moles of carbon dioxide.

The Avogadro constant = 6.02 × 10²³ per mole.

Give your answer to 3 significant figures.

Metal M forms a metal oxide with the formula M₂O₃

The relative formula mass of the metal oxide is 152.

Determine the identity of metal M.

Relative atomic mass ($A_r$): O = 16

This question is about ammonia.

Nitrogen gas reacts with hydrogen gas to produce ammonia gas in a reversible reaction.

The equation for the reaction is:

N₂(g) + 3H₂(g) ⇌ 2NH₃(g)

What is the effect of increasing the pressure on the equilibrium position in this reaction?

Select your answer.

The reaction to produce ammonia gas is exothermic.

What is the effect of increasing the temperature on the relative amount of ammonia at equilibrium?

Select your answer.

Ammonia reacts with hydrogen chloride to produce ammonium chloride (NH₄Cl).

The equation for the reaction is:

NH₃ + HCl → NH₄Cl

6.8 g of ammonia reacts with excess hydrogen chloride.

Explain why ammonia is described as the limiting reactant in this reaction.

Calculate the maximum mass of ammonium chloride that could be produced from 6.8 g of ammonia.

Relative atomic masses (A_r): N = 14, H = 1, Cl = 35.5

Sulfuric acid has the formula H₂SO₄

What is the total number of atoms in the formula H₂SO₄?

0.5 dm³ of a solution of sulfuric acid contains 9.8 g of sulfuric acid.

Calculate the concentration of the solution of sulfuric acid.

Use the equation:

$\text{concentration}=\frac{\text{mass of sulfuric acid}}{\text{volume of solution}}$

The formula of calcium chloride is CaCl₂

Calculate the relative formula mass (M_r) of calcium chloride.

Relative atomic masses (A_r): Ca = 40    Cl = 35.5

98 g of a hydrocarbon contains 84 g of carbon.

The relative formula mass (M_r )of the hydrocarbon is 28.

Relative atomic masses (A_r ): C = 12 H = 1

Determine the formula of the hydrocarbon molecule.

You should determine:

• the simplest whole number mole ratio of carbon : hydrogen

• the empirical formula

• the formula of the hydrocarbon molecule.

This question is about acids, alkalis and salts.

A solution of sodium hydroxide has a concentration of 7.24 g/dm³.

Calculate the mass of sodium hydroxide needed to make 0.25 dm³ of the solution.

Sodium hydroxide reacts with sulfuric acid to produce sodium sulfate (Na₂SO₄) and water.

Write a balanced equation for this reaction.

___________ + ___________ $\to$ ___________ + _____________

The formula of water is H₂O.

Calculate the relative formula mass (M_r) of water.

Relative atomic masses (A_r): H = 1, O = 16.

This question is about the elements magnesium, oxygen and lithium.

What is the type of bonding in magnesium?

Tick (✓) one box.

Magnesium atoms react with oxygen atoms to produce magnesium oxide.

Magnesium oxide contains magnesium ions and oxide ions.

Figure 8 shows the electronic structure of the atoms and the ions.

Only the outer shell electrons are shown.

Describe what happens when a magnesium atom reacts with an oxygen atom to produce a magnesium ion and an oxide ion.

Answer in terms of electrons.

Lithium is an element in Group 1 of the periodic table.

Figure 9 shows a piece of lithium stored in oil.

Suggest why lithium is stored in oil.

A teacher reacted 0.5 g of lithium with oxygen.

The teacher measured the mass of lithium oxide produced.

The teacher repeated the experiment with different masses of lithium.

Table 2 shows the results.

Table 2

Describe the relationship between the mass of lithium reacted and the mass of lithium oxide produced.

Complete Figure 10.

You should:

• label the x-axis

• plot the data from Table 2

• draw a line of best fit.

The teacher did the experiment four times using 0.25 g of lithium.

Table 3 shows the results.

Table 3

Calculate mean value X in Table 3.

Hydrogen (H₂) reacts with chlorine (Cl₂) to produce hydrogen chloride (HCl).

Balance the equation for the reaction.

H₂ + Cl₂ → _ HCl

0.8 g of hydrogen reacts with chlorine to produce 29.2 g of hydrogen chloride.

Calculate the mass of chlorine that reacts.

Mass = ____________________ g

A student electrolysed copper sulfate solution using inert electrodes.

Figure 8 shows the apparatus used.

Figure 8

Copper was produced at the negative electrode.

Oxygen was produced at the positive electrode.

Describe the observations seen at each electrode.

The student measured how the mass of copper produced varied with time.

Table 1 shows the results.

Table 1

What conclusion can be made about how the mass of copper produced varied with time?

Use Table 1.

Predict the time taken to produce 0.20 g of copper.

Use Table 1.

0.5 dm³ of a solution of copper sulfate contains 3.2 g of copper sulfate.

Calculate the concentration of the solution of copper sulfate.

Use the equation:

concentration = mass of copper sulfate / volume of solution

Choose the unit from the box.

Copper sulfate has the formula CuSO₄.

Calculate the percentage (%) by mass of copper in CuSO₄.

Give your answer to 3 significant figures.

Relative atomic mass (A_r): Cu = 63.5

Relative formula mass (M_r): CuSO₄ = 159.5

Complete the equation for the reaction of lithium with water.

You should balance the equation.

Li + H₂O → _____________ + _____________

Potassium is produced at the negative electrode.

Write the half equation for the reaction at the negative electrode during the electrolysis of molten potassium chloride.

____________ + __________ $\to$_________

50 cm³ of potassium chloride solution contains 0.030 moles of potassium chloride.

Calculate the concentration of the potassium chloride solution in g/dm³.

Relative formula mass (M_r) of potassium chloride = 74.5

The formula of nitric acid is HNO₃.

Which expression gives the percentage (%) by mass of oxygen in HNO₃?

Relative atomic mass (A_r): O = 16

Relative formula mass (M_r): HNO₃ = 63

Tick one box.

Magnesium chloride is a salt.

Calculate the number of magnesium ions in 47.5 g of magnesium chloride (MgCl₂).

Relative atomic masses (A_r): Mg = 24, Cl = 35.5

Avogadro constant = 6.02 × 10²³ per mole

Formulae and equations are used to describe chemical reactions.

Aluminium reacts with sulfuric acid (H₂SO₄) to produce aluminium sulfate, Al₂(SO₄)₃, and hydrogen (H₂).

Complete and balance the equation for this reaction.

____Al + ___________ $\to$ ____________ + __________

Calcium carbonate reacts with nitric acid to produce calcium nitrate.

Calculate the relative formula mass (M_r) of calcium nitrate, Ca(NO₃)₂.

Relative atomic masses (A_r): N = 14; O = 16; Ca = 40

Relative formula mass (M_r) =

Zinc carbonate decomposes when heated.

A student heated 25 g zinc carbonate (ZnCO₃).

Figure 11 shows how he set up the apparatus (a boiling tube containing ZnCO₃ clamped over a Bunsen burner).

The balanced chemical equation for the decomposition reaction is:

ZnCO₃ (s) → ZnO (s) + CO₂ (g)

The student measured the mass of solid product after heating until there was no further change in mass.

The student did the experiment four times. Table 4 shows the results.

Table 4

Calculate the mean mass of the solid product.

Do not use any anomalous results in your calculation.

Mean mass = g

Aluminium is produced from an ore called bauxite.

Bauxite contains aluminium oxide.

Look at Figure 7.

Figure 7

Calculate the percentage of bauxite that is converted into aluminium oxide.

Percentage = _________

Show by calculation that the mass of aluminium produced is less than that expected from 1 950 kg aluminium oxide (Al₂O₃).

You should state the difference in the mass of aluminium expected and the mass of aluminium produced to three significant figures.

Relative atomic masses (A_r): O = 16; Al = 27

Figure 8 shows an electrolysis cell used to extract aluminium.

Figure 8

Why does the carbon anode used in the electrolysis cell need to be continually replaced?

The half equation at the cathode is:

Al³⁺ + 3e^- → Al

Calculate the number of moles of electrons needed to produce 1 000 kg of aluminium.

Give your answer to three significant figures.

Relative atomic mass (A_r): Al = 27

Answer = ______moles

Ammonium nitrate (NH₄NO₃) is produced by reacting ammonia with nitric acid.

A student measured the mass of ammonium nitrate that dissolves in 100 cm³ of water at different temperatures.

Table 3 shows the student's results.

Table 3

Use Table 3 to plot a graph of the solubility of ammonium nitrate on Figure 9.

Figure 9

At 20 °C, 190 g of ammonium nitrate dissolves in 100 cm³ of water.

Calculate the amount of ammonium nitrate (in moles) that dissolves in 1 dm³ of water at 20 °C.

Relative atomic masses (A_r): H = 1; N = 14; O = 16

Amount of dissolved ammonium nitrate = mol