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:
<u>1) Determine the oxidation states of all the elements</u>
a) <u>Reactant side</u>:
- Mg(s): 0, since the oxidation state of pure elements is zero
- Br₂: 0, since the oxidation state of pure elements is zero
b) <u>Product side</u>:
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.
<u>2) Look at the changes:</u>
- 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.
<u>Conclusion:</u>
- 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:
<u>1) Determine the oxidation states of all the elements</u>
a) <u>Reactant side</u>:
- 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) <u>Product side</u>:
- 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.
<u>2) Look at the changes:</u>
- 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.
<u>Conclusion:</u>
- 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
<u>1) Determine the oxidation states of all the elements</u>
a) <u>Reactant side</u>:
- 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) <u>Product side</u>:
- 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.
<u>2) Look at the changes:</u>
- 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.
<u>Conclusion:</u>
- Substance being oxidized: Ni
- Substance being reduced: H