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:

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