Pearson Edexcel International GCSE (9–1) · CHEMISTRY · Unit
Principles of Chemistry
991 practice questions
Topics covered
- States of Matter102 practice questions
- Elements, Compounds and Mixtures69 practice questions
- Atomic Structure108 practice questions
- The Periodic Table103 practice questions
- Chemical Formulae, Equations and Calculations Part 119 practice questions
- Chemical Formulae, Equations and Calculations Part 2144 practice questions
- Ionic Bonding143 practice questions
- Covalent Bonding68 practice questions
- Metallic Bonding19 practice questions
- Electrolysis198 practice questions
Practice questions
411–420 of 423 · Normal
Question 411
3 marks · Normal
Answer and see the solution →A student wants to find out whether substance X is an ionic compound, a covalent compound (non-electrolyte), or an acid using an experiment. She sets up the following experiment in which two carbon electrodes are placed in a solution of substance X, connected to a power supply and a bulb, as shown in the diagram:
Apparatus for testing conductivity. In three separate experiments she uses:
Test Substance in solution Observation A X dissolved in water Bulb does not light up B Molten X Bulb lights up C Aqueous acid Bulb lights up Using the data above, calculate whether substance X is ionic, covalent (non-electrolyte), or an acid. Explain your reasoning.
Question 412
6 marks · Normal
Answer and see the solution →Potassium iodide (KI) is an ionic compound. When heated until molten and electrolysed using inert electrodes, iodine gas is produced at one electrode and potassium metal at the other.
(a)[1 mark]State the ions present in molten potassium iodide.
(b)[1 mark]Write the half-equation for the reaction occurring at the cathode.
(c)[1 mark]Write the half-equation for the reaction occurring at the anode.
(d)[2 marks]State, in terms of electron transfer, which reaction involves reduction and which involves oxidation.
(e)[1 mark]Explain how you can use the mnemonic OILRIG to identify which reaction at the electrodes is oxidation and which is reduction.
Question 413
6 marks · Normal
Answer and see the solution →A student carries out the electrolysis of molten calcium chloride (CaCl2) in a laboratory using inert carbon electrodes.
(a)[2 marks]State what is meant by 'discharging an ion' during electrolysis.
(b)[1 mark]Identify the ions in molten calcium chloride and their movement during electrolysis.
(c)[1 mark]Write the half-equation for the discharge of chloride ions at the anode.
(d)[2 marks]Explain, using electron transfer, what happens to a calcium ion during electrolysis.
Question 414
6 marks · Normal
Answer and see the solution →A student sets up an electrolysis experiment using molten potassium iodide (KI). An external circuit with a bulb lights up when the current is switched on.
(a)[2 marks]State the ions present in molten potassium iodide. Identify which ions move towards the cathode and which move towards the anode during electrolysis.
(b)[1 mark]Write the ionic half-equation for the reaction occurring at the cathode.
(c)[1 mark]Write the ionic half-equation for the reaction occurring at the anode.
(d)[2 marks]For the electrode reaction at the cathode, state whether it is an oxidation or a reduction. Justify your answer using the concept of electron transfer.
Question 415
6 marks · Normal
Answer and see the solution →During the electrolysis of molten calcium chloride (CaCl2), calcium forms at one electrode and chlorine gas is released at the other.
(a)[2 marks]Write the balanced ionic half-equation for the reaction at the electrode where chlorine gas is produced.
(b)[2 marks]Explain what is meant by the term 'discharging an ion' using Ca^2+ or Cl^- as an example from this electrolysis process.
(c)[2 marks]Recall the meaning of the mnemonic OILRIG and use it to decide whether the reaction at the chlorine-producing electrode is an oxidation or a reduction.
Question 416
8 marks · Normal
Answer and see the solution →A student is given a mixture of table salt (sodium chloride) and sand. She wants to separate the components and measure the solubility of sodium chloride at 20°C.
(a)[2 marks]Describe a method the student could use to separate the sand from the salt in the mixture. Include the main steps and the name of each process.
(b)[3 marks]After separation, the student makes a saturated solution of sodium chloride in 50 g of water at 20°C. She filters the solution to remove any excess solid, then evaporates the water and obtains 18.6 g of dry sodium chloride crystals.
Use these results to calculate the solubility of sodium chloride in water (in g per 100 g water) at 20°C.
(c)[1 mark]In a different experiment, the student runs a paper chromatography investigation using three coloured inks from different pens. The chromatogram develops as shown below (all spots and the solvent front are marked by distance from the pencil line):
Chromatogram data Pen Colour Distance moved by spot (cm) Distance moved by solvent front (cm) A blue 2.4 7.0 B red 6.1 7.0 C green 4.2 7.0 Calculate the R_f value for the green dye (Pen C).
(d)[2 marks]Explain how a comparison of R_f values can help identify whether two pens use the same dye.
Question 417
8 marks · Normal
Answer and see the solution →For each gap in the sentences or statements below, write the correct word or phrase. You may use each answer once or not at all.
Word list: solute compound element solution mixture saturated solubility solvent
(a)[1 mark](i) A substance made of only one type of atom is called an _____.
(b)[1 mark](ii) A substance formed when two or more elements chemically combine is a _____.
(c)[1 mark](iii) A _____ contains different substances mixed together, not chemically joined.
(d)[1 mark](iv) The part of a solution that dissolves another substance is the _____.
(e)[1 mark](v) The dissolved solid in a solution is called the _____.
(f)[1 mark](vi) A _____ solution contains as much dissolved solute as possible at a particular temperature.
(g)[2 marks](vii) The _____ of a substance is the maximum mass that dissolves in 100 g of solvent at a specific temperature.
Question 418
8 marks · Normal
Answer and see the solution →A student wants to investigate the solubility of a compound and check whether a white powder she found is a pure substance or a mixture.
(a)[3 marks]Outline an experiment to measure the solubility of a solid in water at 40°C. State the key steps and the measurements you would record.
(b)[2 marks]The student measures the melting point of the powder. She finds that it melts over a range from 76°C to 83°C. Explain what this result suggests about the nature of the powder.
(c)[3 marks]Describe how melting point measurements can be used to distinguish between a pure substance and a mixture. Give an example with data.
Question 419
8 marks · Normal
Answer and see the solution →A mixture of potassium nitrate and sand is supplied to a student. She performs a series of experiments to separate the components and calculate solubility.
(a)[2 marks]Describe the two separation techniques needed to obtain pure, dry potassium nitrate from the mixture.
(b)[3 marks]The student adds the mixture to 40.0 g of water and stirs until no more potassium nitrate dissolves. After filtration, she evaporates the solution to recover 22.8 g of dry potassium nitrate. Calculate the solubility of potassium nitrate in water at this temperature (in g per 100 g water).
(c)[2 marks]If the solubility of potassium nitrate at 60°C is 110 g per 100 g of water, and at 30°C it is 45 g per 100 g water, calculate the mass of potassium nitrate that will crystallise out when a saturated solution containing 110 g of potassium nitrate in 100 g water at 60°C is cooled to 30°C.
(d)[1 mark]State why it is important to use filtration after dissolving the mixture in water.
Question 420
8 marks · Normal
Answer and see the solution →This question is about writing balanced equations (with state symbols) and using them to perform gas volume calculations.
(a)[2 marks]Magnesium reacts with steam to produce magnesium oxide and hydrogen gas. Write a balanced chemical equation for this reaction, including state symbols.
(b)[4 marks]Calculate the maximum volume, in cm³, of hydrogen gas formed at rtp when 3.60 g of magnesium is reacted with excess steam. (Ar: Mg = 24.0; molar volume at rtp = 24,000 cm³ mol⁻¹)
(c)[2 marks]State one reason why the actual volume of hydrogen collected in an experiment might be less than your calculated answer.