OCR GCSE Combined Science A (Gateway) Chemistry Paper 9 Higher November 2020 question paper J250/09

Iron can be made from the reaction of iron(III) oxide with carbon monoxide.

What is the reducing agent in this reaction?

A CO

B CO₂

C Fe

D Fe₂O₃

Relative atomic mass compares the average mass of an atom to which element?

A Carbon

B Hydrogen

C Nitrogen

D Oxygen

The particle model used to describe solids, liquids and gases has some limitations.

Which of the following is not a limitation of the particle model?

A The forces of attraction between particles.

B The number of the particles.

C The size of the particles.

D The space between the particles.

Which ionic equation is balanced correctly?

People use perfumes to make them smell nice.

Look at the table. It shows the percentages of the different ingredients in a perfume.

What is the name given to a mixture, such as perfume, where the ingredients are combined in exact amounts?

A bottle contains 25 g of the perfume.

Calculate the mass of water in 25 g of the perfume.

Suggest why the alcohol evaporates very quickly.

This question is about compounds of magnesium.

Magnesium hydroxide contains magnesium ions, Mg²⁺, and hydroxide ions, OH^–. (a)

Write the formula of magnesium hydroxide.

Magnesium carbonate, MgCO₃, reacts with dilute hydrochloric acid, HCl.

Magnesium chloride, MgCl₂, water and carbon dioxide are made.

Write the balanced symbol equation for the reaction.

A compound of magnesium contains an unknown element, X.

X is an element found in Group 7 of the Periodic Table.

The compound has the formula MgX₂.

The relative formula mass of the MgX₂ is 184.1.

Calculate the relative atomic mass of X. A_r Mg = 24.3

Hydrogen, H₂, and chlorine, Cl₂, react to make hydrogen chloride, HCl.

The reaction is exothermic.

Look at Fig. 13.1. It shows the reaction profile for the reaction.

Complete Fig. 13.1 by filling in the two boxes.

Use the balanced symbol equation to help you.

A student investigates how to make a sample of a pure salt.

His method is shown in Fig. 14.1.

React an excess of copper oxide with 50 cm³ dilute hydrochloric acid. Stage 1

Stage 2 Heat the solution from Stage 1.

Copper oxide is an insoluble compound that neutralises dilute hydrochloric acid.

Name the type of insoluble compound that neutralises an acid to form a salt and water.

Dilute hydrochloric acid is a hazardous chemical.

Describe one safety precaution the student should take when using dilute hydrochloric acid.

Stage 1 uses an excess of copper oxide.

Give a reason why.

Calculate the number of moles of copper oxide, CuO, in 0.500 g.

Give your answer to 3 significant figures.

Use your answer to (d)(i) and the balanced symbol equation to explain why the copper oxide is in excess.

Another student thinks that the method in Fig. 14.1 will not make pure copper chloride.

Explain why this student is correct.

Phosphoric acid, H₃PO₄, is a strong acid.

A student investigates how the pH of a solution of dilute phosphoric acid changes when a solution of calcium hydroxide is slowly added to it from a burette.

The student then calculates the concentration of hydrogen ions as the pH changes.

Table 16.1 shows the results of her experiment.

Explain why phosphoric acid is described as a strong acid.

Explain why the solution of phosphoric acid used is described as dilute.

Complete the balanced symbol equation for the reaction between phosphoric acid and calcium hydroxide.

Explain the term electrolysis.

Electrolysis involves the reactions of cations and anions.

Describe the difference between cations and anions.

The electrolysis of molten potassium chloride makes potassium at the cathode.

Write the balanced half equation for the formation of potassium.

State and explain if this equation shows oxidation or reduction.

Name the product formed at the anode when an aqueous solution of potassium chloride, KC l (aq), is electrolysed.

Give a reason for your answer.