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dybincka [34]
4 years ago
5

Write the oxidation and reduction half reactions;

Chemistry
2 answers:
trasher [3.6K]4 years ago
7 0

Answer:

a.

Fe²⁺ → Fe³⁺ + 1 e⁻

Br₂ + 2 e⁻ → 2 Br⁻

b.

Mg → Mg²⁺ + 2 e⁻

Cr³⁺ + 1 e⁻ →  Cr²⁺

Explanation:

a.

Fe is oxidized and its oxidation number increases from 2+ to 3+, according to the following oxidation half-reaction.

Fe²⁺ → Fe³⁺ + 1 e⁻

Br is reduced and its oxidation number decreases from 0 to 1-, according to the following reduction half-reaction.

Br₂ + 2 e⁻ → 2 Br⁻

b.

Mg is oxidized and its oxidation number increases from 0 to 2+, according to the following oxidation half-reaction.

Mg → Mg²⁺ + 2 e⁻

Cr is reduced and its oxidation number decreases from 3+ to 2+, according to the following reduction half-reaction.

Cr³⁺ + 1 e⁻ →  Cr²⁺

luda_lava [24]4 years ago
3 0

Answer:

a)

Fe^{2+}⇒Fe^{3+}+e^-

Br_2+2e^-⇒2Br^-

b)

Mg⇒Mg^{2+}+2e^-

Cr^{3+}+e^-⇒Cr^{3+}

Explanation:

A)

Remember that positive number superscripts mean electrons lack and negative numbers mean electrons 'excess' (if we compare it with the neutral element). So, for the case of Fe2+ which is converted to Fe3+, we know that in Fe2+ there is a two electrons lack, while in Fe3+ there is a 3 electrons lack; it means that Fe2+ was converted to Fe3+ but releasing one electron:

Fe^{2+}⇒Fe^{3+}+e^-

The same analysis is applied to Br2; Br2 is a molecule which is said to have a zero superscript because it is an apolar covalent bond; and it is converted to Br-, which, according to what I wrote above, means that there is a one electron excess. So, Br2 must have received an electron in order to change to Br-; but Br2 can't change to Br- as simple as that because Br2 is a molecule, not an atom; it is a molecule that has two Br atoms, so, Br2 must give two Br- ions as products, but receiving one electron for each one:

Br_2+2e^-⇒2Br^-

b)

Applying the same, in Mg2+ there is a 2 electrons lack, and in Mg is not electron lack (its superscript is zero), so Mg must have released two electrons in order to change to Mg2+:

Mg⇒Mg^{2+}+2e^-

Cr3+ has a 3 electrons lack, and Cr2+ a two electrons one, so, Cr3+ must receive an electron to convert to Cr2+:

Cr^{3+}+e^-⇒Cr^{3+}

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ehidna [41]

<u>Answer: </u>The molar mass of solute is 115 g/mol.

<u>Explanation:</u>

Elevation in the boiling point is defined as the difference between the boiling point of the solution and the boiling point of the pure solvent.

The expression for the calculation of elevation in boiling point is:

\text{Boiling point of solution}-\text{boiling point of pure solvent}=i\times K_b\times m

OR

\text{Boiling point of solution}-\text{Boiling point of pure solvent}=i\times K_f\times \frac{m_{solute}\times 1000}{M_{solute}\times w_{solvent}\text{(in g)}} ......(1)

where,

Boiling point of pure solvent (benzene) = 80.10^oC

Boiling point of solution = 81.20^oC

i = Vant Hoff factor = 1 (for non-electrolytes)

K_b = Boiling point elevation constant = 2.53^oC/m

m_{solute} = Given mass of solute = 10 g

M_{solute} = Molar mass of solute = ? g/mol

w_{solvent} = Mass of solvent = 200 g

Putting values in equation 1, we get:

81.20-80.10=1\times 2.53\times \frac{10\times 1000}{M_{solute}\times 200}\\\\M_{solute}=\frac{1\times 2.53\times 10\times 1000}{1.1\times 200}\\\\M_{solute}=115g/mol

Hence, the molar mass of solute is 115 g/mol.

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3 years ago
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