Edexcel GCSE Combined Science Paper 4: Chemistry 2 Higher November 2021 question paper 1SC0/2CH

The concentration of a solution can be calculated using the equation

A student dissolved 9.25 g of ammonium chloride in water and made up the

Use the equation to calculate the concentration of this solution in gdm⁻³.

concentration =_........ g dm^–3

Dissolving ammonium chloride in water is an endothermic process. Figure 1 shows part of the reaction profile for this process.

Explain how Figure 1 shows that dissolving ammonium chloride in water is an endothermic process.

Complete the reaction profile in Figure 1 and label the activation energy.

Diesel oil is a mixture of hydrocarbons that can be obtained from crude oil.

State the name of the process used to separate diesel oil from crude oil.

Diesel oil contains alkanes. These alkanes are part of an homologous series.

Which statement about compounds in this homologous series is true?

When fuels such as diesel oil are burned, the high temperatures produced can cause nitrogen and oxygen in the air to form the pollutant nitrogen dioxide.

Complete the balanced equation for the reaction.

N₂ + 2O_{2 ........}

Explain how the greenhouse effect is caused by the gases produced by the complete combustion of diesel oil.

This question is about potassium and zinc.

Which of the following temperatures is most likely to be the melting point of potassium?

Explain how the electronic configuration of an atom of potassium is related to its position in the periodic table.

Potassium reacts with oxygen to form potassium oxide.

Describe the test to show that a gas is oxygen.

Potassium oxide is ionic.

Write the electronic configurations for the ions in potassium oxide, K₂O.

potassium ion:_........

oxide ion:_........

Figure 4 shows two gas syringes connected by a glass tube.

Inside the glass tube there are some pieces of zinc. Zinc reacts with oxygen at a temperature of over 225 °C. Not all the oxygen reacts at once, the oxygen reacts only when in contact with the zinc.

Devise a plan to find the volume of oxygen contained in a known volume of air, using the apparatus shown in Figure 4.

This question is about the rate of reaction between calcium carbonate and dilute hydrochloric acid.

The word equation for this reaction is

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

Which of the following is the formula for calcium carbonate?

Some pieces of calcium carbonate were added to dilute hydrochloric acid in a conical flask and the volume of carbon dioxide produced was measured.

Complete the diagram in Figure 5 to show the apparatus to collect the gas produced and measure its volume.

The reaction between calcium carbonate and dilute hydrochloric acid was investigated at different temperatures.

State what could be used to keep the temperature of the conical flask and its contents at a temperature of 45 °C throughout the reaction.

Figure 6 shows a graph of volume of gas collected in this investigation.

Draw a tangent at 100 seconds on Figure 6. Use this tangent to calculate the rate of reaction at this time.

rate of reaction =_........ cm³ s^–1

The temperature of the acid was kept at 45 °C.

State one other variable that needs to be controlled during this investigation.

Explain, in terms of particles, how decreasing the temperature affects the rate of this reaction.

This question is about some of the elements in group 7 of the periodic table.

Which row in the table correctly shows the colours and physical states of the elements at room temperature?

The compound phosphorus oxychloride has the formula POCl₃.

Calculate the percentage by mass of chlorine in phosphorus oxychloride.

(relative atomic masses: O = 16.0, P = 31.0, C l = 35.5)

percentage by mass of chlorine =_........

When iron reacts with chlorine, iron chloride is formed.

Two possible equations for this reaction are

A Fe + Cl₂ FeCl₂ B 2Fe + 3Cl₂ 2FeCl₃

In an experiment, 8.40 g iron reacts with chlorine to form 19.05 g iron chloride.

Show, using a calculation, which reaction, A or B, is taking place.

You must show your working.

(relative atomic masses: C l = 35.5, Fe = 56.0)

*(d) Group 1 metals react with the elements from group 7 to form salts.

Some examples of these reactions are shown in Figure 7.

You will find the position of these elements in their groups on the periodic table.

Explain, in terms of their electronic configurations and the relative reactivity of these elements, which of the reactions shown in Figure 7 would be the most violent.

Pentadecane, C₁₅H₃₂, is a hydrocarbon and is used as a fuel.

The incomplete combustion of pentadecane produces carbon monoxide. Carbon monoxide is a toxic gas.

Explain why the incomplete combustion of pentadecane can produce carbon monoxide as one of the products.

Explain how carbon monoxide behaves as a toxic gas.

1 mole of pentadecane can be cracked to form 1 mole of octane, C₈H₁₈, and 1 mole of propene, C₃H₆, and 2 moles of another product.

Complete the balanced equation for this reaction by adding the formula of the missing product.

C₁₅H₃₂ C₈H₁₈ + C₃H₆ + 2_........

Figure 8 shows the reaction of propene, C₃H₆, with water.

Figure 9 shows some bond energies.

Use the bond energies in Figure 9 to calculate the energy change of the reaction in Figure 8.

energy change of reaction =_........ kJ mol^–1

Methane gas, CH₄, was burned using the apparatus shown in Figure 10.

Explain why water droplets form on the bottom of the beaker of cold water.