Redox Reactions quiz

The oxidation number of Mn in KMnO4 is:

In the reaction Zn + Cu2+ -> Zn2+ + Cu, zinc is:

The oxidation number of oxygen in H2O2 is:

Which of these is a disproportionation reaction?

The strongest reducing agent among these is:

The standard electrode potential of the SHE is:

The oxidation number of Cr in K2Cr2O7 is:

In a Daniell cell, the anode is made of:

The number of electrons gained by one MnO4- ion when it changes to Mn2+ is:

Which of these is an oxidising agent?

Why is oxidation always accompanied by reduction? (2 marks)

What is the oxidation number of sulphur in S8 and in H2S? (2 marks)

Why does fluorine show only a negative oxidation state? (2 marks)

What is a metal displacement reaction? Give an example. (2 marks)

Why is a salt bridge used in a galvanic cell? (2 marks)

What is the electrochemical series? (2 marks)

Why is H2O2 able to act both as an oxidant and a reductant? (2 marks)

Identify the oxidant and reductant in: 2Na + Cl2 -> 2NaCl. (2 marks)

What is the role of acid in the titration of KMnO4 with oxalic acid? (2 marks)

Balance: Cl2 + OH- -> Cl- + ClO- + H2O. (2 marks)

Calculate the oxidation number of carbon in CH4, CO, CO2 and C6H12O6. (3 marks)

Calculate the average oxidation number of S in Na2S2O3. (3 marks)

20 mL of 0.05 M K2Cr2O7 reacts completely with Fe2+ in acid: Cr2O7 2- + 6Fe2+ + 14H+ -> 2Cr3+ + 6Fe3+ + 7H2O. Calculate the moles of Fe2+ oxidised. (3 marks)

Given E zero values: Ag+/Ag = +0.80 V and Cu2+/Cu = +0.34 V, calculate the EMF of a cell made of these electrodes and write the cell reaction. (3 marks)

Calculate the oxidation number of N in HNO3, NO2, N2O and NH3. (3 marks)

Read the passage and answer the questions. When a zinc rod is placed in copper sulphate solution, the blue colour of the solution fades, and a reddish-brown deposit forms on the rod. The reverse process does not occur when copper is placed in zinc sulphate solution. (i) Which species is oxidised and which is reduced? (ii) Why does the blue colour fade? (iii) Why does the reverse not occur? (5 marks)

Read the passage and answer the questions. In acidic medium, potassium permanganate oxidises ferrous ions to ferric ions. The pink colour of permanganate disappears until all ferrous ions are oxidised. After this, a single drop of excess KMnO4 makes the solution light pink. (i) Write the balanced ionic equation. (ii) What is the role of KMnO4 here? (iii) Why is no external indicator needed? (5 marks)

Read the passage and answer the questions. The Daniell cell is a galvanic cell in which zinc and copper electrodes are dipped in solutions of their salts, connected by a salt bridge. The cell converts the chemical energy of a redox reaction into electrical energy. (i) Write the half-reactions at the anode and cathode. (ii) What is the standard EMF of this cell? (iii) What happens if the salt bridge is removed? (5 marks)

Read the passage and answer the questions. When chlorine gas is passed through cold dilute sodium hydroxide, sodium chloride and sodium hypochlorite are formed. Chlorine is both oxidised and reduced in the reaction. (i) What type of redox reaction is this? (ii) Write the change in oxidation number of chlorine. (iii) Name one use of sodium hypochlorite. (5 marks)

Read the passage and answer the questions. The oxidation number of an element in a compound is the charge it would carry if all its bonds were ionic. In Fe3O4, the oxidation number of iron is found to be +8/3. This is because it is a mixed oxide containing iron in two oxidation states. (i) What are the two oxidation states of iron in Fe3O4? (ii) Can an oxidation number be fractional? (iii) Calculate the oxidation number of S in S4O6 2-. (5 marks)

Explain the classical and electronic concepts of oxidation and reduction with examples. What is the oxidation number concept? (6 marks)

State the rules for assigning oxidation numbers and calculate the oxidation numbers of elements in various compounds and ions. (6 marks)

Explain the types of redox reactions with examples. (6 marks)

Explain the oxidation number method and the half-reaction method of balancing redox reactions with examples in acidic and basic media. (6 marks)

Explain the electrode processes and the Daniell cell. What are standard electrode potentials, and how do they predict the feasibility of reactions? (6 marks)