9. Redox Processes SL

June 10, 2021 Shveta 0 Comments ibdp chemistry, Redox Processes

1.Which statement is correct?

Oxidation involves loss of electrons and a decrease in oxidation state
Oxidation involves gain of electrons and an increase in oxidation state
Reduction involves loss of electrons and an increase in oxidation state
Reduction involves gain of electrons and a decrease in oxidation state

2. What occurs during the operation of a voltaic cell based on the following reaction? Ni(s) + Pb2+(aq) → Ni2+(aq) + Pb(s)

	External circuit	Ion movement in solution
A.	electrons move from Ni to Pb	Pb2+(aq) move away from Pb(s)
B.	electrons move from Ni to Pb	Pb2+(aq) move toward Pb(s)
C.	electrons move from Pb to Ni	Ni2+(aq) move away from Ni(s)
D.	electrons move from Pb to Ni	Ni2+(aq) move toward Ni(s)

A
B
C
D

3. The oxidation number of chromium is the same in all the following compounds except

Cr(OH)3
Cr2O3
Cr2(SO4)3
CrO3

4. Magnesium is a more reactive metal than copper. Which is the strongest oxidizing agent?

Mg
Mg2+
Cu
Cu2+

5. Which processes occur during the electrolysis of molten sodium chloride? I. Sodium and chloride ions move through the electrolyte. II. Electrons move through the external circuit. III. Oxidation takes place at the positive electrode (anode).

I and II only
I and III only
II and III only
I, II and III

6. What happens to the Cr3+(aq) ion when it is converted to CrO42–(aq)?

Its oxidation number decreases and it undergoes reduction
Its oxidation number decreases and it undergoes oxidation
Its oxidation number increases and it undergoes reduction
Its oxidation number increases and it undergoes oxidation

7. The following reactions are spontaneous as written. Fe(s) + Cd2+(aq) → Fe2+(aq) + Cd(s) Cd(s) + Sn2+(aq) → Cd2+(aq) + Sn(s) Sn(s) + Pb2+(aq) → Sn2+(aq) + Pb(s) Which of the following pairs will react spontaneously? I. Sn(s) + Fe2+(aq) II. Cd(s) + Pb2+(aq) III. Fe(s) + Pb2+(aq)

I only
II only
III only
II and III only

8. What species are produced at the positive and negative electrodes during the electrolysis of molten sodium chloride?

	Positive electrode	Negative electrode
A.	Na+(l)	Cl2(g)
B.	Cl–(l)	Na+(l)
C.	Na(l)	Cl2(g)
D.	Cl2(g)	Na(l)

A
B
C
D

9. Consider the following reaction. H2SO3(aq) + Sn4+(aq) + H2O(l) → Sn2+(aq) + HSO4–(aq) + 3H+(aq) Which statement is correct?

H2SO3 is the reducing agent because it undergoes reduction
H2SO3 is the reducing agent because it undergoes oxidation
Sn4+ is the oxidizing agent because it undergoes oxidation
Sn4+ is the reducing agent because it undergoes oxidation

10. In which change does oxidation occur?

CH3CHO → CH3CH2OH
CrO42–→ Cr2O72–
SO42–→ SO32–
NO2– → NO3–

11. What happens at the positive electrode in a voltaic cell and in an electrolytic cell?

	Voltaic cell	Electrolytic cell
A.	Oxidation	Reduction
B.	Reduction	Oxidation
C.	Oxidation	Oxidation
D.	Reduction	Reduction

A
B
C
D

12. What are the oxidation numbers of the elements in sulfuric acid, H2SO4?

	Hydrogen	Sulfur	Oxygen
A.	+1	+6	–2
B.	+1	+4	–2
C.	+2	+1	+4
D.	+2	+6	–8

A
B
C
D

13. A voltaic cell is made from copper and zinc half-cells. The equation for the reaction occurring in the cell is Zn(s) + Cu2+(aq) → Zn2+(aq) + Cu(s) Which statement is correct when the cell produces electricity?

Electrons are lost from zinc atoms
The mass of the copper electrode decreases
Electrons flow from the copper half-cell to the zinc half-cell
Negative ions flow through the salt bridge from the zinc half-cell to the copper half-cell.

14. What happens when molten sodium chloride is electrolysed in an electrolytic cell?

Chlorine is produced at the positive electrode
Sodium ions lose electrons at the negative electrode
Electrons flow through the liquid from the negative electrode to the positive electrode
Oxidation occurs at the negative electrode and reduction at the positive electrode

15. Which equations represent reactions that occur at room temperature? I. 2Br–(aq) + Cl2(aq) → 2Cl–(aq) + Br2(aq) II. 2Br–(aq) + I2(aq) → 2I–(aq) + Br2(aq) III. 2I–(aq) + Cl2(aq) → 2Cl–(aq) + I2(aq)

I and II only
I and III only
II and III only
I, II and III

16. Which equation represents a redox reaction?

KOH(aq) + HCl(aq) → KCl(aq) + H2O(l)
Mg(s) + 2HCl(aq) → MgCl2(aq) + H2(g)
CuO(s) + 2HCl(aq) → CuCl2(aq) + H2O(l)
ZnCO3(s) + 2HCl(aq) → ZnCl2(aq) + CO2(g) + H2O(l)

17. The following information is given about reactions involving the metals X, Y and Z and solutions of their sulfates. X(s) + YSO4(aq) → no reaction Z(s) + YSO4(aq) → Y(s) + ZSO4(aq) When the metals are listed in decreasing order of reactivity (most reactive first), what is the correct order?

Z > Y > X
X > Y > Z
Y > X > Z
Y > Z > X

18. What are the oxidation numbers of the elements in the compound phosphoric acid, H3PO4?

	Hydrogen	Phosphorus	Oxygen
A.	+1	+1	–2
B.	+1	+5	–2
C.	+3	+1	–4
D.	+3	+5	–8

A
B
C
D

19. A voltaic cell is made from magnesium and iron half-cells. Magnesium is a more reactive metal than iron. Which statement is correct when the cell produces electricity?

Electrons are lost from magnesium atoms
The concentration of Fe2+ ions increases
Electrons flow from the iron half-cell to the magnesium half-cell
Negative ions flow through the salt bridge from the magnesium half-cell to the iron half-cell

20. Which are examples of reduction? I. Fe3+ becomes Fe2+ II. Cl– becomes Cl2 III. CrO3 becomes Cr3+

I and II only
I and III only
II and III only
I, II and III

21. Which statement is correct for the electrolysis of a molten salt?

Positive ions move toward the positive electrode
A gas is produced at the negative electrode
Only electrons move in the electrolyte
Both positive and negative ions move toward electrodes

22. Which statement about the following reaction is correct? 2Br–(aq) + Cl2(aq) → Br2(aq) + 2Cl–(aq)

Br–(aq) is reduced and gains electrons
Cl2(aq) is reduced and loses electrons
Br–(aq) is oxidized and loses electrons
Cl2(aq) is oxidized and gains electrons

23. Consider the following spontaneous reactions. Fe(s) + Cu2+(aq) → Fe2+(aq) + Cu(s) Cu(s) + 2Ag+(aq) → Cu2+(aq) + 2Ag(s) Zn(s) + Fe2+(aq) → Zn2+(aq) + Fe(s) Which is the correct combination of strongest oxidizing agent and strongest reducing agent?

	Strongest oxidizing agent	Strongest reducing agent
A.	Ag(s)	Zn(s)
B.	Ag+(aq)	Zn(s)
C.	Zn2+(aq)	Ag(s)
D.	Zn(s)	Ag+(aq)

A
B
C
D

24. In which change does nitrogen undergo oxidation?

NO2 → N2O4
NO3– → NO2
N2O5→ NO3–
NH3 → N2

25. Which statement is correct?

Spontaneous redox reactions produce electricity in an electrolytic cell
Electricity is used to carry out a non-spontaneous redox reaction in a voltaic cell
Oxidation takes place at the negative electrode in a voltaic cell and the positive electrode in an electrolytic cell
Oxidation takes place at the negative electrode in a voltaic cell and reduction takes place at the positive electrode in an electrolytic cell

26. The compound [Co(NH3)5Br]SO4 is isomeric with the compound [Co(NH3)5SO4]Br. What is the oxidation state of cobalt in these compounds?

	[Co(NH3)5Br]SO4	[Co(NH3)5SO4]Br
A.	+3	+3
B.	+2	+1
C.	+3	+2
D.	+2	+3

A
B
C
D

27. What happens to vanadium during the reaction VO2+(aq) → VO3–(aq)?

It undergoes oxidation and its oxidation number changes from +4 to +5
It undergoes oxidation and its oxidation number changes from +2 to +4
It undergoes reduction and its oxidation number changes from +2 to –1
It undergoes reduction and its oxidation number changes from +4 to +2

28. What occurs during the electrolysis of a molten salt?

Electricity is produced by a spontaneous redox reaction
Electricity is used to cause a non-spontaneous redox reaction to occur
Electrons flow through the molten salt
Electrons are removed from both ions of the molten salt

29. Which statement is correct about an oxidizing agent in a chemical reaction?

It reacts with oxygen
It reacts with H+ ions
It loses electrons
It undergoes reduction

30. Which formula represents an aldehyde?

CH3CH2CHO
CH3COCH3
CH3CH2COOH
CH3CH2COOH

31. What is the reducing agent in this reaction? Cu(s) + (aq) + 4H+(aq) → Cu2+(aq) + 2NO2(g) + 2H2O(l)

Cu(s)
(aq)
Cu2+(aq)
H+(aq)

32. A particular voltaic cell is made from magnesium and iron half-cells. The overall equation for the reaction occurring in the cell is Mg(s) + Fe2+(aq) → Mg2+(aq) + Fe(s) Which statement is correct when the cell produces electricity?

Magnesium atoms lose electrons
The mass of the iron electrode decreases
Electrons flow from the iron half-cell to the magnesium half-cell
Negative ions flow through the salt bridge from the magnesium half-cell to the iron half-cell

33. What process occurs at the cathode in a voltaic cell and at the anode in an electrolytic cell?

	Cathode of voltaic cell	Anode of Electrolytic cell
A.	Oxidation	Reduction
B.	Oxidation	Oxidation
C.	Reduction	Oxidation
D.	Reduction	Reduction

A
B
C
D

34. Consider the following reaction: H2SO3(aq) + Sn4+(aq) + H2O(l) → Sn2+(aq) + HSO4–(aq) + 3H+(aq) Which statement is correct?

35. Which processes occur during the electrolysis of molten sodium chloride? I. Sodium and chloride ions move through the electrolyte. II. Electrons move through the external circuit. III. Oxidation takes place at the anode.

I and II only
I and III only
II and III only
I, II and III

Sciences for IGCSE & IB

9. Redox Processes SL

Leave a Reply Cancel reply