Edexcel GCSE Combined Science Paper 3: Chemistry 1 Higher June 2023 question paper 1SC0/1CH

In an experiment, powdered calcium hydroxide was added to dilute hydrochloric acid and the pH was measured.

The method used was

step 1 measure 200 cm3³ dilute hydrochloric acid into a beaker

step 2 aadd 0.1 g of powdered calcium hydroxide to the beaker

step 3 find the pH of the mixture

step 4 repeat steps 2 and 3 until the pH stops changing.

State what should be done after step 2 to make sure that any reaction is complete.

Complete the word equation for the reaction.

calcium hydroxide + hydrochloric acid _........

Which row of the table shows the state symbols for powdered calcium hydroxide and dilute hydrochloric acid in the balanced chemical equation?

The results of the experiment are shown in Figure 1.

mass of calcium hydroxide added in grams

Figure 1

Using Figure 1, give the pH of the acid at the start of the experiment.

pH =_........

Using Figure 1, give the mass of calcium hydroxide required to make a neutral mixture.

mass of calcium hydroxide =_........ g

Explain why the pH starts at a low value and ends at a higher value.

Figure 2 shows part of the reactivity series of metals.

Which metal reacts when added to cold water?

A student investigates the reactivity of four different metals.

The student adds an equal‑sized piece of each metal to separate test tubes containing dilute hydrochloric acid.

The student’s observations for zinc and copper are recorded in Figure 3.

Use the information in Figure 2 and in Figure 3 to predict the observations for the reactions of magnesium and of iron with dilute hydrochloric acid.

magnesium

iron

When metals react with acids, hydrogen gas is produced.

Describe the test to show that the gas is hydrogen.

When magnesium reacts with hydrochloric acid, magnesium chloride and hydrogen are formed.

Complete the balanced equation for the reaction.

Mg +_........ HCl MgCl₂ +_........

An excess of magnesium is added to some dilute hydrochloric acid of pH 2. The mass of hydrogen gas produced is measured.

The experiment is repeated with excess magnesium but with the same volume of dilute hydrochloric acid of pH 1.

State how many times greater the concentration of hydrogen ions is in the acid of pH 1 than in the acid of pH 2.

With the acid of pH 2, the mass of hydrogen gas produced when the reaction is complete is 0.005 g.

Predict the mass of hydrogen gas produced in the reaction with acid of pH 1.

mass =_........ g

Ammonia is manufactured in the Haber process by the reversible reaction between nitrogen and hydrogen.

Write the balanced equation for the reversible reaction between nitrogen and hydrogen to make ammonia, NH₃.

Which row shows the typical conditions of temperature and pressure used in the Haber process?

In the Haber process, iron is added to the vessel where the nitrogen and hydrogen react.

State the purpose of the iron.

The reaction between nitrogen and hydrogen to make ammonia can reach dynamic equilibrium.

The reaction gives out heat.

Explain how the position of equilibrium changes if the temperature is decreased.

Compound A is a dark brown gas.

Compound B is a colourless gas.

Two molecules of A combine to form one molecule of B in a reversible reaction.

You are given

• a sealed glass tube containing an equilibrium mixture of A and B

• a beaker

• a kettle

• some ice

At room temperature, the equilibrium mixture is a pale brown colour.

Devise an experiment to show how the position of equilibrium of this reaction is affected by temperature.

The sealed tube must not be opened.

A student investigates the mass of copper produced when copper chloride solution in a beaker is electrolysed using inert electrodes.

Where is copper formed during the electrolysis?

The student investigated the change in the mass of copper formed when the current was altered.

The results are shown in Figure 4.

State and explain the trend shown in these results.

Describe how, after the power supply has been switched off, the mass of copper formed can be measured.

In another experiment, 74 mg of copper is formed.

Calculate the number of copper atoms in 74 mg of copper.

(relative atomic mass Cu = 63.5; Avogadro constant = 6.0210²³)

number of atoms =_........

Crystals of copper sulfate are prepared by reacting copper oxide, a base, with dilute sulfuric acid.

Name the other product of this reaction.

During the experiment, a spatula measure of copper oxide, a black powder, is added to warm, dilute sulfuric acid in a beaker.

When the mixture is stirred, the black powder disappears and the mixture turns pale blue.

The student then adds more copper oxide until the maximum amount of copper sulfate is formed without wasting copper oxide.

Explain how the student knows when to stop adding copper oxide.

The reaction produces an aqueous solution of copper sulfate.

What is the best way to obtain crystals of copper sulfate from an aqueous solution?

When some water is removed from the aqueous solution of copper sulfate, crystals of copper sulfate are made.

Describe how the arrangement and movement of the particles change as crystals are formed from a solution.

In this reaction, copper oxide, CuO, forms copper sulfate, CuSO₄.

Explain, in terms of electrons, whether the copper in copper oxide has been oxidised, has been reduced, or has not been oxidised or reduced.

In another experiment, a copper sulfate solution with a concentration of 39.875 g dm^–3 is used.

Calculate the mass of copper sulfate dissolved in 0.300 dm³ of this solution.

mass =_........ g

Figure 5 shows the structure of a molecule of compound S.

Use Figure 5 to deduce the empirical formula of compound S.

The melting points of three samples of S are shown in Figure 6.

State whether each of these samples, A, B and C, is pure or impure and justify your answers using the information in Figure 6.

A scientist uses chromatography in an investigation of compound S.

In the conditions used, compound S has an R_f value of 0.22.

Calculate the distance the spot of compound S moves if the solvent front has moved by 2.4 cm.

distance =_........ cm

*(c) A solution of sodium chloride in water needs to be separated to obtain a sample of pure, dry sodium chloride and a sample of pure water.

Figure 7 shows the boiling points of sodium chloride and water.

Explain this difference in boiling points in terms of the structure and bonding of sodium chloride and water and how this difference is used to choose a method to separate sodium chloride solution into pure, dry sodium chloride and pure water.