Acids & Alkalis (AQA GCSE Combined Science: Synergy: Physical Sciences): Exam Questions

This question is about acids and alkalis.

Magnesium reacts with acids to produce a salt and hydrogen.

The ionic equation for the reaction is:

Mg + 2H⁺ → Mg²⁺ + H₂

In a redox reaction, both oxidation and reduction occur.

Explain why this reaction is described as a redox reaction.

What happens to the pH of an acid when the hydrogen ion concentration decreases by a factor of ten?

Select your answer.

Write the ionic equation that represents the neutralisation reaction between an acid and an alkali in aqueous solution.

You should include state symbols.

Potassium reacts with water to form a solution with a pH of 13.

Explain why the solution has a pH of 13.

You should refer to ions in your answer.

Figure 12 shows four models representing the same volume of:

• a strong acid at two different concentrations

• a weak acid at two different concentrations.

[IMAGE: Figure 12 — Four models labelled W, X, Y and Z showing particles in containers. Each model shows different numbers and types of particles (ionised and un-ionised) representing different acids at different concentrations.]

Which model represents the weak acid with the higher concentration?

Select your answer.

Justify your answer.

Give two limitations of using the models in Figure 12 to represent acids.

This question is about acids and alkalis.

Universal indicator is used to measure the pH of solutions.

Which is a pH value of an alkaline solution?

Which is a colour of universal indicator in an alkaline solution?

What piece of equipment measures the pH of a solution more accurately than universal indicator?

Which ion do all acids produce in aqueous solution?

The reaction between an acid and an alkali produces water.

What is the name of this type of reaction?

Calcium reacts with hydrochloric acid.

The word equation for the reaction is:

calcium + hydrochloric acid → calcium chloride + hydrogen

Which state symbol is used for the hydrogen produced in this reaction?

TABLE 4 shows the mass of calcium chloride produced when different masses of calcium react with hydrochloric acid.

TABLE 4

Complete the sentence.

Use TABLE 4.

As the mass of calcium reacted increases, the mass of calcium chloride produced __________________________ .

Complete FIGURE 11.

You should:

• label the y-axis

• plot the data from TABLE 4

• draw a line of best fit.

The point at 0.0, 0.0 has been plotted for you.

FIGURE 11

Predict the mass of calcium chloride produced when 1.25 g of calcium reacts with hydrochloric acid.

Use FIGURE 11.

Mass of calcium chloride = ___________ g

Copper carbonate reacts with hydrochloric acid to produce copper chloride and two other products.

Name the TWO other products formed when copper carbonate reacts with hydrochloric acid.

Do NOT refer to copper chloride.

Describe a method to make pure, dry crystals of copper chloride from copper carbonate and hydrochloric acid.

A student investigated the reaction between citric acid powder and sodium hydrogen carbonate solution.

The temperature of the reaction mixture decreased.

Plan a method to investigate how changing the mass of citric acid affects the lowest temperature reached by the mixture.

The reaction between citric acid and sodium hydrogen carbonate is endothermic.

Which reaction profile represents an endothermic reaction?

Tick (✓) one box.

Explain why the rate of reaction is greater when powder is used instead of larger lumps.

Refer to surface area and collisions in your answer.

What is meant by a 'weak acid'?

Name ONE weak acid.

The pH value of a solution decreases by one.

How does the hydrogen ion concentration of this solution change?

Tick (✓) ONE box.

The salt copper sulfate can be made by reacting copper carbonate with dilute sulfuric acid.

CuCO₃(s) + H₂SO₄(aq) → CuSO₄(aq) + H₂O(l) + CO₂(g)

Write a method that a student could use to prepare a pure, dry sample of copper sulfate.

You do not need to write a risk assessment or include safety points.

Calculate the number of molecules in 14 g of carbon dioxide.

Give your answer in standard form.

Relative atomic masses (Aᵣ): C = 14; O = 16

Answer = molecules

(Use the Avogadro constant: 1 mole = 6.02 × 10²³ molecules.)

This question is about acids and salts.

Nitric acid is a strong acid.

A solution of nitric acid can be dilute.

Explain how nitric acid can be both strong and dilute.

The pH value of a solution of nitric acid increases by 1.

How does the hydrogen ion concentration of the solution change?

Tick (✓) one box.

A student reacted nitric acid with excess calcium carbonate.

The word equation for the reaction is:

calcium carbonate + nitric acid → calcium nitrate + water + carbon dioxide

This is the method used.

1. Measure 100 cm³ of nitric acid into a beaker.

2. Add calcium carbonate powder to the nitric acid.

3. Stir the mixture.

4. Repeat steps 2 and 3 until the calcium carbonate is in excess.

5. Filter the mixture.

Describe the additional steps that should be included in the method to determine the mass of calcium carbonate that reacted.

What is the formula of calcium nitrate?

Use the periodic table.

Tick (✓) one box.

Excess hydrochloric acid in the stomach can cause pain. The excess hydrochloric acid can be neutralised by a calcium carbonate tablet.

A student investigated how the pH changed when a calcium carbonate tablet was added to hydrochloric acid.

This is the method used.

1. Add 10 cm³ of hydrochloric acid to a beaker.

2. Measure the pH of the hydrochloric acid using an indicator.

3. Add a calcium carbonate tablet to the hydrochloric acid.

4. Time for 3 minutes.

5. Measure the pH of the mixture using an indicator.

Which two of the following pieces of equipment are needed in this method?

Tick (✓) two boxes.

Name an indicator used to measure pH.

Name a piece of equipment that gives a more accurate pH value than an indicator.

The word equation for the reaction is:

calcium carbonate + hydrochloric acid → calcium chloride + water + carbon dioxide

Why is fizzing seen during the reaction?

Give one safety precaution the student should have taken.

What is the pH of a neutral solution?

Tick (✓) one box.

A student reacted hydrochloric acid with excess calcium carbonate.

A solution of calcium chloride was produced.

Figure 5 shows the method used to produce calcium chloride crystals from the reaction mixture.

Describe the method shown in Figure 5 to produce calcium chloride crystals from the reaction mixture.

Include the equipment used.

Acids produce hydrogen ions in aqueous solutions.

What is the ionic equation for neutralisation reactions?

Tick (✓) one box.

Sulfuric acid reacts with copper carbonate to produce a salt, water and carbon dioxide.

What is the name of the salt produced?