Edexcel GCSE Combined Science Paper 3: Chemistry 1 Higher November 2021 question paper 1SC0/1CH

The scientist John Dalton lived over 200 years ago.

John Dalton suggested an early model of atoms.

When Dalton first described atoms he said that

• all elements are made of atoms

• atoms are not formed of any smaller particles

• all atoms of the same element are identical.

Give two differences between Dalton’s model of atoms and today’s model of atoms.

Dalton also investigated different gases.

One of the gases that Dalton investigated was ethene.

The structure of one molecule of ethene is shown in Figure 1.

Give the molecular formula and the empirical formula of ethene.

molecular formula_........

empirical formula_........

Another gas that Dalton investigated was chlorine.

Chlorine gas reacts with water. The two products are a solution of hydrogen chloride and the substance HC l O.

Complete the balanced equation for this reaction, including the three missing state symbols.

Hydrogen chloride solution is acidic.

The formulae of four ions are shown in Figure 2.

Give the formula of the ion in Figure 2 that causes the hydrogen chloride solution to be acidic.

formula_........

An acid reacts with an alkali.

Give the name of this type of reaction.

A sample of potable water contains impurities.

Why is this sample of water potable even though it contains impurities?

Waste water can be used to produce drinking water. The processes used include sedimentation, filtration and chlorination.

What is sedimentation?

State why the waste water is filtered.

State the reason for chlorination.

Some salts can be added to waste water to remove impurities. In an experiment, different masses of salt A were added to 1000cm³ samples of waste water. The experiment was repeated with salt B. The percentages of impurities removed from the waste water are shown in Figure 3.

mass of salt in mg per 1000cm³ water

Figure 3

It was concluded that the best way to purify 1000cm³ of the waste water is to add 100 mg of salt B.

Use the information about salt A and salt B in Figure 3 to evaluate this conclusion.

Waste water may contain phosphate ions, PO₄^3-.

Aluminium ions react with phosphate ions to form aluminium phosphate.

Complete the ionic equation for the formation of aluminium phosphate in this reaction.

_........ + PO₄^3- _........

This question is about electrolysis.

A sample of molten potassium bromide is electrolysed.

What are the two products formed?

Zinc chloride and zinc carbonate contain ions.

Zinc chloride mixed with water can be electrolysed. Zinc carbonate mixed with water cannot be electrolysed.

Explain this difference.

In the electrolysis of sodium chloride solution, bubbles of a colourless gas form at the cathode. This gas, when mixed with air, burns with a squeaky pop.

Identify this gas.

Explain how this gas is formed at the cathode.

A solution of copper sulfate in a beaker is electrolysed using copper electrodes.

Draw a labelled diagram to show how this experiment would be set up.

The beaker has been drawn for you.

During the electrolysis, the anode gets smaller, the cathode gets larger and the solution remains the same shade of blue.

Give the reason for each of these observations.

the anode gets smaller_........

the cathode gets larger_........

the solution remains the same shade of blue_........

Copper carbonate reacts with dilute nitric acid.

During the reaction the copper carbonate powder completely disappears.

State what can be deduced about the amount of acid used.

During the reaction, the pH of the mixture changed from 2 to 6.

By what factor has the concentration of the hydrogen ions in the mixture changed?

Using different reactants, a solution of copper sulfate was prepared.

Describe what should be done to obtain copper sulfate crystals from this copper sulfate solution.

Hydrated copper sulfate has the formula CuSO₄.5H₂O. The formula tells us that each mole of copper sulfate contains 5 moles of water.

A sample of CuSO₄.5H₂O was heated gently until all the water was removed to form anhydrous copper sulfate, CuSO₄.

The mass of water formed was 4.5 g.

Calculate the mass of hydrated copper sulfate that was heated.

(relative atomic masses: H = 1.0, O = 16.0; relative formula mass: CuSO₄.5H₂O = 249.5)

mass of CuSO₄.5H₂O =_........ g

The order of reactivity of copper, magnesium and zinc can be determined by the displacement reactions between these metals and solutions of their salts.

You are provided with

• samples of the three metals

• solutions of copper sulfate, magnesium sulfate and zinc sulfate.

Describe the experiments that can be done to determine the order of reactivity of these metals by displacement reactions.

Metals can be extracted from ores found in the Earth’s crust.

Explain why aluminium cannot be extracted from its ore by heating with carbon but can be extracted by electrolysis.

Titanium is extracted from its ore in several stages.

In the first stage, titanium chloride is formed as a gas.

The gas is cooled to form liquid titanium chloride containing dissolved impurities.

Suggest how pure titanium chloride could be separated from the impurities.

In another stage, the pure titanium chloride, TiCl₄, is reacted with 500 moles of magnesium, an excess.

Calculate the number of moles in 45 000 grams of titanium chloride.

(relative atomic masses: C l = 35.5, Ti = 48.0)

number of moles titanium chloride =_........

Show that the 500 moles of magnesium added is an excess.

After this reaction, there is a mixture of the solids magnesium, titanium and magnesium chloride.

Titanium does not react with dilute hydrochloric acid.

Suggest a simple method to separate titanium from the mixture.

An ion of element X can be represented as

This ion of element X has 54 electrons.

Calculate the number of protons and the number of neutrons in this ion.

number of protons_........

number of neutrons_........

A sample of silicon contains isotopes.

State, in terms of subatomic particles, how atoms of these isotopes are the same.

This sample of silicon contains three isotopes.

92% of the atoms are silicon-28 5% of the atoms are silicon-29 3% of the atoms are silicon-30

Calculate the relative atomic mass of silicon in this sample.

relative atomic mass =_........

*(c) Figure 4 shows some properties of three substances, A, B and C.

Deduce, using the information in Figure 4, the structure and bonding of substances A, B and C, explaining their properties in terms of their structure and bonding.