Edexcel GCSE Combined Science Paper 4: Chemistry 2 Foundation November 2020 question paper 1SC0/2CF

The two most common gases in today’s atmosphere are nitrogen and oxygen.

What is the third most common gas in today’s atmosphere?

What is the percentage of oxygen in today’s atmosphere?

Give the name of the most common gas in the Earth’s early atmosphere.

This early atmosphere was hot and contained water vapour. The atmosphere today contains less water vapour.

Explain what caused the amount of water vapour in the atmosphere to decrease.

The concentration of carbon dioxide in the atmosphere can be measured in parts per million (ppm).

Figure 1 shows the measurements in January 2018 and January 2019.

Calculate the increase in the concentration, in ppm, of carbon dioxide from January 2018 to January 2019.

Give your answer to the nearest whole number.

increase in concentration of carbon dioxide =_........ ppm

Give a possible cause for this increase in the concentration of carbon dioxide.

A student investigated the reaction between potassium iodide and lead nitrate.

Solutions of potassium iodide and lead nitrate were mixed together. Lead iodide and potassium nitrate were formed.

Complete the word equation.

The student recorded the total mass of the reactants and the total mass of the products.

The results are shown in Figure 2.

State how the results in Figure 2 show that mass is conserved in this reaction.

In another experiment, a student investigated the temperature decrease when different amounts of ammonium nitrate crystals were dissolved in 100 cm³ of water.

The apparatus used is shown in Figure 3.

The student used the following method.

step N $pour 100 cm³ of water into the polystyrene cup

step 2 add one spatula of ammonium nitrate crystals to the water

step 3 stir the mixture

step 4 use the thermometer to record the lowest temperature reached by the mixtur e

step 5 repeat steps 1 to 4 using different amounts of ammonium nitrate

Name a piece of apparatus that should be used to measure the 100 cm³ of water in step 1.

The student cannot work out the temperature decrease using the method described.

State what the student must do before step 2 to be able to work out the temperature decrease.

State why a polystyrene cup is used in this experiment.

Figure 4 shows the reaction profile for this reaction.

Use the words from the box to complete the labels on Figure 4.

Chlorine, bromine and iodine are elements in group 7 of the periodic table.

Chlorine is toxic.

State one safety precaution that should be taken when using chlorine in the laboratory.

Chlorine reacts with hydrogen to form hydrogen chloride.

Write the word equation for this reaction.

Hydrogen chloride dissolves in water to form an acidic solution.

State what is seen when blue litmus paper is placed into this solution.

A chlorine atom has seven electrons in its outer shell. A hydrogen atom has one electron in its outer shell.

Complete the dot and cross diagram of a molecule of hydrogen chloride. Show outer shell electrons only.

Name the type of bonding in a molecule of hydrogen chloride.

If chlorine solution is added to sodium bromide solution a reaction occurs.

chlorine + sodium bromide sodium chloride + bromine

Give a reason why this reaction occurs.

Figure 5 shows apparatus used to find out if a solution conducts electricity.

Glucose solution and sodium chloride solution are tested. Glucose is a typical simple molecular covalent compound. Sodium chloride is an ionic compound.

State what would happen to the lamp when glucose solution is tested.

State what would happen to the lamp when sodium chloride solution is tested.

Figure 6 shows how the conductivity of one solution changes as its concentration increases.

Figure 6

Describe how the conductivity of this solution changes as its concentration increases from 0 to 500 g dm^–3.

Methane is a hydrocarbon fuel.

Complete the word equation for the complete combustion of methane in oxygen.

methane +_........ water +_........

The incomplete combustion of methane can produce carbon and carbon monoxide.

Give the reason why carbon and carbon monoxide are produced in the incomplete combustion of methane.

Crude oil is a complex mixture of hydrocarbons. Crude oil can be separated into useful fractions by fractional distillation.

Figure 7 shows a fractional distillation column and the fractions produced when crude oil is distilled.

Name the fraction in Figure 7 that is used to surface roads.

Name the fraction in Figure 7 that contains hydrocarbons with the lowest boiling point.

When crude oil is fractionally distilled, the demand for some fractions is more than the amount produced.

Figure 8 shows the relative amounts of each fraction in a crude oil and the relative demand for each of these fractions.

Which of the following shows the fractions where the relative demand is greater than the relative amount in the crude oil?

Cracking involves the breaking down of large hydrocarbon molecules into smaller hydrocarbon molecules.

Octane, C₈H₁₈, can be cracked to produce one molecule of ethene, C₂H₄, and one molecule of C_xH₁₄.

Determine the value of x in the molecule of C_xH₁₄.

x =_........

Dodecane is a large hydrocarbon molecule. When one molecule of dodecane is cracked the products are one molecule of octane and one molecule of butene.

dodecane octane + butene

Calculate the maximum mass of octane that could be produced when 340 g of dodecane is cracked in this reaction.

(relative formula masses: dodecane = 170, octane = 114)

mass of octane =_........ g

An atom of potassium has atomic number 19 and mass number 39.

Give the electronic configuration of this potassium atom.

This potassium atom forms the ion K⁺.

Which row shows the number of protons and the number of neutrons in this potassium ion, K⁺?

Potassium and caesium are in the same group of the periodic table.

Explain, in terms of electrons, why potassium and caesium are in the same group.

Fluorine boils at –188C. There are forces between fluorine molecules.

Explain, in terms of these forces, why the boiling point of fluorine is low.

Potassium reacts with fluorine to form potassium fluoride. Potassium fluoride is a solid.

Complete the balanced equation for this reaction and add the state symbols.

_........ K (_........ ) + F₂(g) _........ KF (_........ )

What are the elements in group 1 of the periodic table called?

Figure 9 shows the melting points and boiling points of elements in group 7 of the periodic table.

Give, using Figure 9, the boiling point of bromine.

boiling point of bromine =_........ C

State which two elements from Figure 9 are solids at room temperature.

Calcium carbonate reacts with dilute hydrochloric acid to produce carbon dioxide gas.

The rate of reaction between calcium carbonate and dilute hydrochloric acid at room temperature was investigated.

The investigation was carried out with different sized calcium carbonate pieces.

The mass of calcium carbonate and all other conditions were kept the same.

The results are shown in Figure 10.

State, using the information in Figure 10, the effect of the surface area of the calcium carbonate on the rate of this reaction.

The calcium carbonate powder produced 90 cm³ of carbon dioxide in five minutes.

Calculate the average rate of reaction in cm³s^–1.

average rate of reaction =_........ cm³s^–1

The experiments were repeated at a higher temperature. The rate of reaction for each experiment increased.

Explain, in terms of particles, why the rate of reaction increased when the temperature was increased.

*(b) Zinc metal reacts with dilute hydrochloric acid to produce hydrogen gas.

zinc + hydrochloric acid zinc chloride + hydrogen

A student investigated the effect of doubling the concentration of the hydrochloric acid on this reaction.

The student made the following prediction.

Devise a plan, including the apparatus you would use, to test the student’s prediction.

You are provided with pieces of zinc and two bottles of dilute hydrochloric acid. One bottle of hydrochloric acid is double the concentration of the other.