Question

For each reaction, identify the substance being oxidized and the substance being reduced.?A.)Mg(s)+Br2(g)→MgBr2(s) substance being oxidized: substance being reduced: B.)2Cr3+(aq)+3Mn(s)→2Cr(s)+3Mn2+(aq) substance being oxidized: substance being reduced: C.)2H+(aq)+Ni(s)→H2(g)+Ni2+(aq) substance being oxidized: substance being reduced:

Answer 1

These are three questions each with its complete answer.

A.)  Mg(s) + Br₂(g) → MgBr₂(s)

Answer:

• substance being oxidized: Mg

• substance being reduced: Br

Explanation:

1) Determine the oxidation states of all the elements

a) Reactant side:

• Mg(s): 0, since the oxidation state of pure elements is zero

• Br₂: 0, since the oxidation state of pure elements is zero

b) Product side:

• MgBr₂(s):

        Br, such as the other halogens, form metal halides with oxidation state -1

        Mg, such as other earth alkalyn metals, use oxidation state +2

        Verify that the compound is neutral: 2 (-1) + 2 = 0.

2) Look at the changes:

• Mg passed from 0 to +2. Increase on the oxidation state means oxidation.

• Br passed from 0 to - 1. Decrease on the oxidation state means reduction.

Conclusion:

• Substance being oxidized: Mg

• Substance being reduced: Br

B.) 2Cr³⁺(aq) + 3Mn(s) → 2Cr(s) + 3Mn²⁺(aq)

Answer:

• substance being oxidized: Mn

• substance being reduced: Cr

Explanation:

1) Determine the oxidation states of all the elements

a) Reactant side:

• Cr: +3, since it is indicated as a superscript to the right of the symbol.

• Mn: 0, since the oxidation state of pure elements is zero

b) Product side:

• Cr: 0, since the oxidation state of the pure elements is zero.

• Mn: +2, since it is indicated as s superscript to the right of the atom.

2) Look at the changes:

• Cr passed from +3 to 0. Decrease on the oxidation state means reduction.

• Mn passed from 0 to + 2. Increase on the oxidation state means oxidation.

Conclusion:

• Substance being oxidized: Mg

• Substance being reduced: Br

C.) 2H⁺ (aq) + Ni(s) → H₂(g) + Ni²⁺ (aq)

• substance being oxidized: Ni

• substance being reduced: H

1) Determine the oxidation states of all the elements

a) Reactant side:

• H: +1, since it is understood a number 1 in front of the + symbol to rright of the chemical symbol.

• Ni: 0, since the oxidation state of pure elements is zero

b) Product side:

• H₂(g): 0, since the oxidation state of the pure elements is zero.

• Ni: +2, since it is indicated as s superscript to the right of the ion.

2) Look at the changes:

• H passed from +1 to 0. Decrease on the oxidation state means reduction.

• Ni passed from 0 to + 2. Increase on the oxidation state means oxidation.

Conclusion:

• Substance being oxidized: Ni

• Substance being reduced: H