Leaving Cert Chemistry - Oxidation and Reduction

Which one of the following species loses an electron in the chemical reaction shown?
Mg + Cu²⁺ --> Mg²⁺ + Cu
1. Mg
2. Cu²⁺
3. Mg²⁺
4. Cu
Oxidation is defined as the loss of electrons. In the following equation, which species is oxidised?
2Na + Cl₂ --> 2NaCl
1. Na
2. Cl₂
3. 2NaCl
4. None of them is oxidised
Which one of the following species loses one or more electrons in the chemical reaction shown?
Mg + Cu²⁺ --> Mg²⁺ + Cu
1. Mg
2. Cu²⁺
3. Mg²⁺
4. Cu
Which of the following statements is correct?
1. A reducing agent loses electrons in a redox reaction
2. The oxidising agent is always oxidised in a redox reaction
3. The oxidising agent always loses electrons
4. The reducing agent is reduced in a redox reaction
The following reaction takes place when zinc is placed in a copper sulfate solution:
Zn + Cu²⁺ --> Zn²⁺ + Cu
Which one of these species is the oxidising agent?
1. Zn
2. Cu²⁺
3. Zn²⁺
4. Cu
Which one of the following substances is a good oxidising agent?
1. hydrogen peroxide
2. water
3. sulfur dioxide
4. coke (carbon)
Which one of the following reactions is NOT a redox reaction?
1. 2Mg + O₂ --> 2MgO
2. Zn + Cu²⁺ --> Zn²⁺ + Cu
3. HCl + NaOH --> NaCl + H₂O
4. I₂ + 2Fe²⁺ --> 2I^- + 2Fe³⁺
Of the halogens, which one is the most powerful oxidising agent?
1. fluorine
2. chlorine
3. bromine
4. iodine
A colourless solution of chlorine is mixed with a colourless solution of potassium bromide (KBr). What colour does the resultant mixture turn?
1. red
2. yellow
3. colourless
4. green
A green solution of iron sulfate is placed in a test-tube and chlorine water added. The colour of the expected mixture is most likely to be
1. brown
2. green
3. colourless
4. red
In the electrochemical series, metals are arranged in order of their tendency to
1. lose electrons
2. react with water
3. become reduced
4. release halogens from their salts
Of the following metals, which one will lose electrons the easiest?
1. Potassium
2. Copper
3. Magnesium
4. Zinc
A substance that has the ability to conduct electricity when dissolved in water is known as
1. an electrolyte
2. an electrode
3. a cathode
4. an anode
What is the name given to the charged species that are attracted to the negative electrode in an electrolyte?
1. cations
2. cathode
3. anions
4. anode
In the electrolysis of copper sulfate solution using copper electrodes, which one of the following reactions takes place at the cathode?
1. Cu²⁺ + 2e^- --> Cu
2. Cu --> Cu²⁺ + 2e^-
3. 2H₂O + 2e^- --> H₂O + 2OH^-
4. 2H⁺ + 2e^- --> H₂
In the electrolysis of acidified water, what is the correct equation for the reaction that takes place at the anode?
1. 2H₂O --> 4H⁺ + O₂ + 4e^-
2. 4H⁺ + 4e^- --> 2H₂
3. 2H₂ + O₂ --> 2H₂O
4. 2H₂O --> 2H₂ + O₂
When a solution of sodium sulfate is electrolysed using universal indicator solution, what colours will appear at the cathode and the anode?
1. purple at the cathode and red at the anode
2. red at the cathode and purple at the anode
3. brown at the cathode and red at the anode
4. green at the cathode and brown at the anode
Phenolphthalein indicator is colourless in an acid and turns pink in an alkaline solution. When an aqueous solution of potassium iodide is electrolysed with phenolphthalein indicator, what colours appear at the electrodes?
Cathode: 2H₂O_(l) + 2e^- ---> H_(g) + 2OH^-_(aq)
Anode: 2I^-_(aq) ---> I_2(s) + 2e^-
1. pink at the cathode and brown at the anode
2. brown at the anode and colourless at the cathode
3. brown at the cathode and pink at the anode
4. red at the cathode and pink at the anode
Which one of the following is NOT a practical application of electrolysis?
1. plating steel with chromium
2. plating silver onto nickel cutlery
3. purifying copper
4. purifying steel
What electrolyte is used to electroplate silver onto a spoon?
1. silver nitrate
2. pure water
3. copper sulfate
4. acidified water
What is the oxidising agent in the following reaction?
2Fe²⁺_(aq) + Cl_2(g) ---> 2Fe³⁺_(aq) + 2Cl^-_(aq)
1. Cl_2(g)
2. Fe²⁺_(aq)
3. Fe³⁺_(aq)
4. Cl^-_(aq)
Which one of the following shows the correct order for increasing tendency to lose electrons in the electrochemical series?
1. Copper, lead, zinc and sodium
2. Silver, tin, potassium and magnesium
3. Potassium, sodium, lead and gold
4. Sodium, calcium, tin and silver
When a piece of magnesium ribbon is placed in a beaker of copper sulfate solution, which one of the following is most likely to happen?
1. The blue colour of the copper sulfate solution gets lighter.
2. The blue colour of the copper sulfate solution gets darker.
3. A vigorous reaction immediately takes place, with the release of a lot of heat.
4. The magnesium catches fire.
What is the name given to a solution, or liquid that conducts electricity?
1. Electrolyte
2. Anion
3. Cathode
4. Electrode
When water is electrolysed by adding dilute sulfuric acid into the Hofmann Voltameter, which one of the following statements is incorrect?
1. Cations are attracted to the positive anode.
2. The ratio of hydrogen: oxygen produced is 2:1
3. Dilute sulfuric acid is added to the water to improve its conductivity.
4. Hydrogen ions in the solution move towards the cathode
When an electric current is passed through an electrolyte, which of the following carries this current through the electrolyte?
1. Ions
2. Electrons
3. Atoms
4. Molecules
In which one of the following reactions is chlorine oxidised?
1. F₂ + 2Cl^-_(aq) ---> Cl_2(aq) + 2F^-_(aq)
2. 2ClO₃^- + 12H⁺ + 10e^- ---> Cl₂ + 6H₂O
3. 2Na_(s) + Cl_2(g) ---> 2NaCl_(s)
4. Cl₂ + 2e^- --->2Cl^-

Leaving Cert Chemistry - Oxidation and Reduction

Multiple Choice Quiz