Question 1

What is the oxidation number of chlorine in sodium perchlorate, NaClO₄?

Accepted Answer

The oxidation number of sodium is +1 (since it's an alkali metal).
The oxidation number of oxygen is -2 (unless it's in a peroxide, where it's -1).
We can set up the equation:

(+1) + x + (-2 x 4) = 0 (the sum of oxidation numbers in a compound should be 0)

Simplifying we get:

+1 + x - 8 = 0

Solving for x we get:

x = +7

Therefore, the oxidation number of chlorine in NaClO4 is +7.

Question 2

Examine the following reaction: 5FeCl₂(aq)+ KMnO₄(aq)+ 8HCl(aq)→ 5FeCl₃(aq)+ MnCl₂(aq)+ KCl(aq)+ 4H₂O(l)Which element has undergone oxidation?

Accepted Answer

Fe changes from Fe^2+ to Fe^3+, indicating it loses an electron and undergoes oxidation.

Question 3

Consider the reaction: CH₄(g)+ 2O₂(g)→ CO₂(g)+ 2H₂O(g)Which of the following statements is correct?

Accepted Answer

Carbon is oxidized because its oxidation number increases from -4 to +4.

Question 4

Consider the reaction: H₂O(l)+ 3SO₃²⁻(aq)+ 2MnO₄⁻(aq)→ 3SO₄²⁻(aq)+ 2MnO₂(s)+ 2OH⁻(aq)Which species is reduced?

Accepted Answer

The reduction half-reaction is MnO4- + 8H+ + 5e- -> Mn2+ + 4H2O. In the given reaction, MnO4- gains 5 electrons to become Mn2+, which means it has undergone reduction. Therefore, species C, MnO(S2O8)2-4 is reduced.

Question 5

Consider the following reaction: 2Fe³⁺(aq)+ 2Hg(l)+ 2Cl⁻(aq)→ 2Fe²⁺(aq)+ Hg₂Cl₂(s)In this reaction,

Accepted Answer

The answer of Consider the following reaction: 2Fe³⁺(aq)+ 2Hg(l)+ 2Cl⁻(aq)→...

Question 6

Consider the reaction: H₂O(l)+ 3SO₃²⁻(aq)+ 2MnO₄⁻(aq)→ 3SO₄²⁻(aq)+ 2MnO₂(s)+ 2OH⁻(aq)Which species is the reducing agent?

Accepted Answer

The answer of Consider the reaction: H₂O(l)+ 3SO₃²⁻(aq)+ 2MnO₄⁻(aq)→ 3SO₄²⁻(aq)+...

Question 7

In which of the following does chlorine have an oxidation number of +3?

Accepted Answer

The answer of In which of the following does chlorine...

Question 8

The change, Br₂ + H₂O → HOBr + HBr, is

Accepted Answer

The change involves the transfer of electrons from Br to O, which is oxidation, and from H to Br, which is reduction. Therefore, it is both oxidation and reduction.

Question 9

What are the oxidation numbers of the atoms in the AsO₄^3- ion?

Accepted Answer

In the given ion, arsenic (As) is in its highest oxidation state due to its position in the compound, which is +5. Oxygen (O), as is common in most compounds, has an oxidation state of -2. This is consistent with the general rules of oxidation states where oxygen is almost always -2 except in peroxides and fluorine compounds, and the oxidation state of arsenic can vary across different compounds, reaching up to +5 in more oxidized forms.

Question 10

Which of the following sulfur species cannot be further reduced?

Accepted Answer

The answer of Which of the following sulfur species cannot...

Question 11

What is the oxidation number of boron in sodium tetraborate, Na₂B₄O₇?

Accepted Answer

In sodium tetraborate (Na2B4O7), the oxidation number of boron can be calculated by considering the overall charge of the compound and the known oxidation states of the other elements. Sodium (Na) has an oxidation state of +1, and oxygen (O) has an oxidation state of -2. The formula Na2B4O7 implies there are 2 sodium atoms (+2 total), 7 oxygen atoms (-14 total), and the compound is neutral. Solving for the oxidation state of boron (B) gives us +3 when the algebraic sum of the oxidation states is set to zero for a neutral compound.

Question 12

What are the oxidation numbers of the atoms in the Cr₂O₇²⁻ ion?

Accepted Answer

To determine oxidation numbers, we first need to identify the elements present and their known oxidation states. From the formula, we can see that there are four elements present: Cr, S, U, and O. The oxidation states of S and P can be assumed to be -2 and +5, respectively.

For Cr, we can use the rule that the sum of oxidation numbers in a neutral compound is 0. We also know that the oxidation state of oxygen is usually -2, so there are a total of (-2 x 17) = -34 electrons from the O atoms. Summing up the oxidation states of the other elements should give us 34 to balance the equation.

Let x be the oxidation state of Cr, and y be the oxidation state of U. Thus, we have:
x + (-2 x 17) + y + (-2) + (5 x 12) - 2 = 0
x + y - 4 = 0
x + y = 4

From here, we can only make assumptions about the oxidation state of U, as it is not known. However, we do know that the oxidation state of Cr must be positive, as it is combining with negatively charged S and O atoms.

Option A can be eliminated, as this would mean the oxidation state of Cr is negative, which is not possible. Option B can also be eliminated, as there is no reason to believe that the oxidation state of O is -2 in this case. Option D can be eliminated, as a Cr oxidation state of +7 is not commonly observed.

Therefore, the best choice is C, where the oxidation state of Cr is +6 and the oxidation state of O is -2 to balance the charge.

Question 13

Consider the reaction: N₂(g)+ 3H₂(g)→ 2NH₃(g)Which of the following statements is correct?

Accepted Answer

In the given reaction, hydrogen is gaining electrons and getting reduced to form NH. Therefore, hydrogen is acting as the reducing agent. Nitrogen, on the other hand, is losing electrons and getting oxidized to form NH. Therefore, nitrogen is the oxidizing agent. Thus, option E is the correct choice.

Question 14

Consider the reaction: H₂O(l)+ 3SO₃^2-(aq)+ 2MnO₄^-(aq)→ 3SO₄^2-(aq)+ 2MnO₂(s)+ 2OH^-(aq)Which species is oxidized?

Accepted Answer

Sulfite ion (SO3^2-) is oxidized as it goes from a +4 oxidation state in SO3^2- to a +6 oxidation state in sulfate ion (SO4^2-).

Question 15

Examine the following reaction: 5FeCl₂(aq)+ KMnO₄(aq)+ 8HCl(aq)- 5FeCl₃(aq)+ MnCl₂(aq)+ KCl(aq)+ 4H₂O(l)Which element has undergone reduction?

Accepted Answer

The answer of Examine the following reaction: 5FeCl₂(aq)+ KMnO₄(aq)+ 8HCl(aq)-...

Question 16

Consider the reaction: Ca(s)+ 2H₂O(l)→ Ca(OH)₂(aq)+ H₂(g)Which of the following statements is correct?

Accepted Answer

In the given reaction, calcium (Ca) is oxidized. It loses electrons and forms calcium hydroxide (Ca(OH)2) which has a +2 charge compared to neutral calcium (Ca). Oxygen (O) is neither reduced nor oxidized as its oxidation state remains -2 on both sides of the equation. Therefore, options A, B, C, and D are incorrect.

Question 17

Consider the following oxidation-reduction reaction: 2Fe³⁺(aq)+ 2Hg(l)+ 2Cl⁻(aq)→ 2Fe²⁺(aq)+ Hg₂Cl₂(s)Which one of the following pairs correctly indicates the oxidizing agent and the reducing agent in this reaction? Oxidizing agent Reducing agent

Accepted Answer

In the given reaction, FeS undergoes oxidation to FeS2 while Hg undergoes reduction to HgS. Therefore, FeS is the reducing agent and Hg is the oxidizing agent. Option D correctly pairs FeS and Hg as the reducing and oxidizing agents, respectively.

Question 18

Consider the reaction: 2HgO(s)→ 2Hg(l)+ O₂(g)Which of the following statements is correct?

Accepted Answer

- Mercury goes from a positive oxidation state in HgO to a zero oxidation state in Hg, which means it gains electrons and is reduced.
- Oxygen goes from a zero oxidation state in HgO to a negative oxidation state in O2, which means it loses electrons and is oxidized.
- Mercury(II) ion is the oxidizing agent because it causes the oxidation of oxygen.
- Oxide ion is the reducing agent because it causes the reduction of mercury. Therefore, all statements A, B, C, and D are correct.

Question 19

Consider the reaction: Ba(NO₃)₂(aq)+ Na₂SO₄(aq)→ BaSO₄(s)+ 2NaNO₃(aq)Which of the following statements is correct?

Accepted Answer

This reaction is a double displacement reaction, not an oxidation-reduction reaction. The oxidation states of all elements remain unchanged throughout the reaction.

Question 20

What is the oxidation number of sulfur in S₂O₃^2-?

Accepted Answer

The answer of What is the oxidation number of sulfur...

Quiz 14: Oxidation-Reduction Reactions

What is the oxidation number of chlorine in sodium perchlorate, NaClO₄?

Examine the following reaction: 5FeCl₂(aq) + KMnO₄(aq) + 8HCl(aq) → 5FeCl₃(aq) + MnCl₂(aq) + KCl(aq) + 4H₂O(l) Which element has undergone oxidation?

Consider the reaction: CH₄(g) + 2O₂(g) → CO₂(g) + 2H₂O(g) Which of the following statements is correct?

Consider the reaction: H₂O(l) + 3SO₃²⁻(aq) + 2MnO₄⁻(aq) → 3SO₄²⁻(aq) + 2MnO₂(s) + 2OH⁻(aq) Which species is reduced?

Consider the following reaction: 2Fe³⁺(aq) + 2Hg(l) + 2Cl⁻(aq) → 2Fe²⁺(aq) + Hg₂Cl₂(s) In this reaction,

Consider the reaction: H₂O(l) + 3SO₃²⁻(aq) + 2MnO₄⁻(aq) → 3SO₄²⁻(aq) + 2MnO₂(s) + 2OH⁻(aq) Which species is the reducing agent?

In which of the following does chlorine have an oxidation number of +3?

The change, Br₂ + H₂O → HOBr + HBr, is

What are the oxidation numbers of the atoms in the AsO₄^3- ion?

Which of the following sulfur species cannot be further reduced?

What is the oxidation number of boron in sodium tetraborate, Na₂B₄O₇?

What are the oxidation numbers of the atoms in the Cr₂O₇²⁻ ion?

Consider the reaction: N₂(g) + 3H₂(g) → 2NH₃(g) Which of the following statements is correct?

Consider the reaction: H₂O(l) + 3SO₃^2-(aq) + 2MnO₄^-(aq) → 3SO₄^2-(aq) + 2MnO₂(s) + 2OH^-(aq) Which species is oxidized?

Examine the following reaction: 5FeCl₂(aq) + KMnO₄(aq) + 8HCl(aq) - 5FeCl₃(aq) + MnCl₂(aq) + KCl(aq) + 4H₂O(l) Which element has undergone reduction?

Consider the reaction: Ca(s) + 2H₂O(l) → Ca(OH) ₂(aq) + H₂(g) Which of the following statements is correct?

Consider the following oxidation-reduction reaction: 2Fe³⁺(aq) + 2Hg(l) + 2Cl⁻(aq) → 2Fe²⁺(aq) + Hg₂Cl₂(s) Which one of the following pairs correctly indicates the oxidizing agent and the reducing agent in this reaction? Oxidizing agent Reducing agent

Consider the reaction: 2HgO(s) → 2Hg(l) + O₂(g) Which of the following statements is correct?

Consider the reaction: Ba(NO₃) ₂(aq) + Na₂SO₄(aq) → BaSO₄(s) + 2NaNO₃(aq) Which of the following statements is correct?

What is the oxidation number of sulfur in S₂O₃^2-?

Quiz 14: Oxidation-Reduction Reactions

What is the oxidation number of chlorine in sodium perchlorate, NaClO4?

Examine the following reaction: 5FeCl2(aq) + KMnO4(aq) + 8HCl(aq) → 5FeCl3(aq) + MnCl2(aq) + KCl(aq) + 4H2O(l) Which element has undergone oxidation?

Consider the reaction: CH4(g) + 2O2(g) → CO2(g) + 2H2O(g) Which of the following statements is correct?

Consider the reaction: H2O(l) + 3SO32−(aq) + 2MnO4−(aq) → 3SO42−(aq) + 2MnO2(s) + 2OH−(aq) Which species is reduced?

Consider the following reaction: 2Fe3+(aq) + 2Hg(l) + 2Cl−(aq) → 2Fe2+(aq) + Hg2Cl2(s) In this reaction,

Consider the reaction: H2O(l) + 3SO32−(aq) + 2MnO4−(aq) → 3SO42−(aq) + 2MnO2(s) + 2OH−(aq) Which species is the reducing agent?

In which of the following does chlorine have an oxidation number of +3?

The change, Br2 + H2O → HOBr + HBr, is

What are the oxidation numbers of the atoms in the AsO43- ion?

Which of the following sulfur species cannot be further reduced?

What is the oxidation number of boron in sodium tetraborate, Na2B4O7?

What are the oxidation numbers of the atoms in the Cr2O72− ion?

Consider the reaction: N2(g) + 3H2(g) → 2NH3(g) Which of the following statements is correct?

Consider the reaction: H2O(l) + 3SO32-(aq) + 2MnO4-(aq) → 3SO42-(aq) + 2MnO2(s) + 2OH-(aq) Which species is oxidized?

Examine the following reaction: 5FeCl2(aq) + KMnO4(aq) + 8HCl(aq) - 5FeCl3(aq) + MnCl2(aq) + KCl(aq) + 4H2O(l) Which element has undergone reduction?

Consider the reaction: Ca(s) + 2H2O(l) → Ca(OH) 2(aq) + H2(g) Which of the following statements is correct?

Consider the following oxidation-reduction reaction: 2Fe3+(aq) + 2Hg(l) + 2Cl−(aq) → 2Fe2+(aq) + Hg2Cl2(s) Which one of the following pairs correctly indicates the oxidizing agent and the reducing agent in this reaction? Oxidizing agent Reducing agent

Consider the reaction: 2HgO(s) → 2Hg(l) + O2(g) Which of the following statements is correct?

Consider the reaction: Ba(NO3) 2(aq) + Na2SO4(aq) → BaSO4(s) + 2NaNO3(aq) Which of the following statements is correct?

What is the oxidation number of sulfur in S2O32-?

What is the oxidation number of chlorine in sodium perchlorate, NaClO₄?

Examine the following reaction: 5FeCl₂(aq) + KMnO₄(aq) + 8HCl(aq) → 5FeCl₃(aq) + MnCl₂(aq) + KCl(aq) + 4H₂O(l) Which element has undergone oxidation?

Consider the reaction: CH₄(g) + 2O₂(g) → CO₂(g) + 2H₂O(g) Which of the following statements is correct?

Consider the reaction: H₂O(l) + 3SO₃²⁻(aq) + 2MnO₄⁻(aq) → 3SO₄²⁻(aq) + 2MnO₂(s) + 2OH⁻(aq) Which species is reduced?

Consider the following reaction: 2Fe³⁺(aq) + 2Hg(l) + 2Cl⁻(aq) → 2Fe²⁺(aq) + Hg₂Cl₂(s) In this reaction,

Consider the reaction: H₂O(l) + 3SO₃²⁻(aq) + 2MnO₄⁻(aq) → 3SO₄²⁻(aq) + 2MnO₂(s) + 2OH⁻(aq) Which species is the reducing agent?

The change, Br₂ + H₂O → HOBr + HBr, is

What are the oxidation numbers of the atoms in the AsO₄^3- ion?

What is the oxidation number of boron in sodium tetraborate, Na₂B₄O₇?

What are the oxidation numbers of the atoms in the Cr₂O₇²⁻ ion?

Consider the reaction: N₂(g) + 3H₂(g) → 2NH₃(g) Which of the following statements is correct?

Consider the reaction: H₂O(l) + 3SO₃^2-(aq) + 2MnO₄^-(aq) → 3SO₄^2-(aq) + 2MnO₂(s) + 2OH^-(aq) Which species is oxidized?

Examine the following reaction: 5FeCl₂(aq) + KMnO₄(aq) + 8HCl(aq) - 5FeCl₃(aq) + MnCl₂(aq) + KCl(aq) + 4H₂O(l) Which element has undergone reduction?

Consider the reaction: Ca(s) + 2H₂O(l) → Ca(OH) ₂(aq) + H₂(g) Which of the following statements is correct?

Consider the following oxidation-reduction reaction: 2Fe³⁺(aq) + 2Hg(l) + 2Cl⁻(aq) → 2Fe²⁺(aq) + Hg₂Cl₂(s) Which one of the following pairs correctly indicates the oxidizing agent and the reducing agent in this reaction? Oxidizing agent Reducing agent

Consider the reaction: 2HgO(s) → 2Hg(l) + O₂(g) Which of the following statements is correct?

Consider the reaction: Ba(NO₃) ₂(aq) + Na₂SO₄(aq) → BaSO₄(s) + 2NaNO₃(aq) Which of the following statements is correct?

What is the oxidation number of sulfur in S₂O₃^2-?