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4.1. Electrolysis
A subsection of Chemistry, 0620, through 4. Electrochemistry
Listing 10 of 449 questions
Electrolysis of concentrated aqueous sodium chloride using inert electrodes forms chlorine, hydrogen and sodiumhydroxide. What is meant by the term electrolysis? Name a substance that can be used as the inert electrodes. Write an ionic half-equation for the formation of hydrogen during this electrolysis. Give the formulae of the four ions present in concentrated aqueous sodium chloride. Explain how sodiumhydroxide is formed during this electrolysis. 
0620_s20_qp_42
THEORY
2020
Paper 4, Variant 2
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Potassium reacts with chlorine to form potassiumchloride, KCl. Write a chemical equation for this reaction. Potassiumchloride is an ionic compound. Complete the diagram to show the electron arrangement in the outer shells of the ions present in potassium chloride. Give the charges on both ions. K Cl  Molten potassiumchloride undergoes electrolysis. State what is meant by the term electrolysis. Name the products formed at the positive electrode and negative electrode when molten potassiumchloride undergoes electrolysis. anode cathode  Concentrated aqueous potassiumchloride undergoes electrolysis. Write an ionic half-equation for the reaction at the negative electrode . Name the product formed at the positive electrode . Name the potassium compound that remains in the solution after electrolysis. Complete the dot-and-cross diagram to show the electron arrangement in a molecule of chlorine, Cl 2. Show the outer electrons only. Cl Cl  The melting points and boiling points of chlorine and potassium chloride are shown. melting point / °C boiling point / °C chlorine –101 –35 potassium chloride Deduce the physical state of chlorine at –75 °C. Use the data in the table to explain your answer. physical state explanation  Explain, in terms of structure and bonding, why potassiumchloride has a much higher melting point than chlorine. Your answer should refer to the: ● types of particle held together by the forces of attraction ● types of forces of attraction between particles ● relative strength of the forces of attraction. 
0620_s21_qp_41
THEORY
2021
Paper 4, Variant 1
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A student carries out an electrolysis experiment using the apparatus shown. + – carbon electrodes wire dilute aqueous sodium chloride The student uses dilute aqueous sodiumchloride. State the name given to any solution which undergoes electrolysis. Hydroxide ions are discharged at the anode. Complete the ionic half-equation for this reaction. OH–→ + O2+ 4e– Explain how the ionic half-equation shows the hydroxide ions are being oxidised. Describe what the student observes at the cathode. Write the ionic half-equation for the reaction at the cathode. The student repeats the experiment using concentrated aqueous sodiumchloride. Describe what the student observes at: ● the cathode ● the anode.  The student added litmus to the solution after the electrolysis of concentrated aqueous sodiumchloride. State the colour seen in the solution. Give a reason for your answer. colour of solution reason  Carbon electrodes are used because they are inert. State another element that can be used instead of carbon. 
0620_s21_qp_42
THEORY
2021
Paper 4, Variant 2
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Questions Discovered
449