Oxidation and Reduction

Q.

Give an example of a redox reaction. Indicate the substance that is oxidized and that is reduced.

Q.

Is losing hydrogen oxidation or reduction?

Q.

What occurs when an atom is oxidized in a chemical reaction?

1. loss of electrons; decrease in O.N.

2. loss of electrons; increase in O.N.

3. gain of electrons; decrease in O.N.

4. gain of electrons; increase in O.N.

Q.

The reducing agent in the following reaction is:
Pb(s) + Cu²⁺(aq) → Pb²⁺ (aq) + Cu(s)

1. Pb²⁺ (aq)

2. Cu²⁺ (aq)

3. Pb (s)

4. Cu (s)

Q.

Identify the following reactions as either oxidation or reduction:

(i) O + 2e^- ⇢ O^2-

Q. Which one among the following is the strongest reducing agent?
$F{e}^{2+}+2e^{-}\to Fe(-0.44V)$
$N{i}^{2+}+2e^{-}\to Ni(-0.25V)$
$S{n}^{2+}+2e^{-}\to Sn(-0.14V)$
$F{e}^{3+}+e^{-}\to F{e}^{2+}(+0.77V)$

1. $Fe$
2. $F{e}^{2+}$
3. $Ni$
4. $Sn$

Q.

Define the term redox reaction.

Q.

Oxidation is the:

1. removal of an electron

2. removal of a non-metal

3. addition of an electron

4. addition of a metal atom

Q.

Give an example of a chemical reaction that is characterized by the production of electricity.

Q. Oxidation state of S in $N{a}_2{S}_2{O}_3$ is

1. 5
2. 0
3. 2
4. -1

Q. In compounds formed by the union of different elements, the more electronegative atom will
have negative oxidation state.

1. True
2. False

Q. Match the following given the reaction below:
$CuO+H_2⟶Cu+H_{2}O$

1. CuO
2. $H_2$
3. Cu
4. $H_{2}O$

Q. In the reaction, $8Al+3F{e}_3{O}_4\to 4A{l}_2{O}_3+9Fe,$ number of electrons transferred from reductant to oxidant is:

1. $4$
2. $24$
3. $16$
4. $8$

Q. Which of the following could be considered to be oxidation?

1. $2H{g}^{2+}+2e^{-}\to H{g}_2^{2+}$
2. $Z{n}^{2+}+2e^{-}\to Zn$
3. $F{e}^{2+}\to F{e}^{3+}+e^{-}$
4. $Mn{O}_4^{2-}\to Mn{O}_4^{-}+e^{-}$

Q. A reducing agent is that substance which itself undergoes reduction in a chemical reaction.

1. True
2. False

Q.

Identify the oxidized and reduced substances in the following reactions.

${\mathrm{H}}_2\left(\mathrm{g}\right)+\mathrm{CuO}\left(\mathrm{s}\right)\to \mathrm{Cu}\left(\mathrm{s}\right)+{\mathrm{H}}_2\mathrm{O}\left(\mathrm{l}\right)$

Q. Number of electrons transfer in each case when $KMn{O}_4$ acts as an oxidizing agent to give $Mn{O}_2,M{n}^{2+},Mn(OH{)}_3,andMn{O}_4^{2-}$ are respectively:

1. 3, 5, 4, and 1
2. 4, 3, 1, and 5
3. 1, 3, 4, and 5
4. 5, 4, 3, and 1

Q.

Breathalyzers detect alcohol via:

Cr₂O₇^2- + C₂H₅OH → Cr³⁺ + CH₃CHO

1. Ethanol - reductant; no oxidant

2. Ethanol - reductant; Cr₂O₇^2- - oxidant

3. Ethanol - oxidant; Cr³⁺ - reductant

4. Ethanol - reductant; Cr³⁺ - oxidant

Q. Which of the following is an oxidising agent in $2Mg+O_2\left(g\right)\to 2MgO\left(s\right)$

1. Mg
2. $O_2$
3. Both Mg and O
4. None of these

Q.

Differentiate between oxidation and reduction

Q. Neutralisation of $HCl\left(aq\right)$ with $NaOH\left(aq\right)$ is an example of a/an reaction.

1. oxidizing
2. reducing
3. redox
4. non-redox

Q.

Explain oxidation and reduction from various perspectives with illustrative examples.

Q.

Consider the following reaction and based on the reaction answer the questions that follow:

$\begin{array}{r}{\left({\mathrm{NH}}_4\right)}_2{\mathrm{Cr}}_2{\mathrm{O}}_7\stackrel{\text{heat}}{⟶}{\mathrm{N}}_2(\mathrm{g})+4{\mathrm{H}}_2\mathrm{O}\left(\mathrm{g}\right)+{\mathrm{Cr}}_2{\mathrm{O}}_3\\ \end{array}$

Calculate:
The quantity in moles of ${\left({\mathrm{NH}}_4\right)}_2{\mathrm{Cr}}_2{\mathrm{O}}_7$ if $63g$ of ${\left({\mathrm{NH}}_4\right)}_2{\mathrm{Cr}}_2{\mathrm{O}}_7$ is heated.

Q. Hydrogen peroxide oxidises $\left[Fe\right(CN{)}_6{]}^{4-}$ to $\left[Fe\right(CN{)}_6{]}^{3-}$ in acidic medium but reduces $\left[Fe\right(CN{)}_6{]}^{3-}$ to $\left[Fe\right(CN{)}_6){]}^{4-}$ in alkaline medium. The other products formed, repectively are:

1. $H_{2}O$ and $(H_{2}O+O{H}^{-})$
2. $(H_{2}O+O_2)$ and $H_{2}O$
3. $(H_{2}O+O_2)$ and $(H_{2}O+O{H}^{-})$
4. $H_{2}O$ and $(H_{2}O+O_2)$

Q. Which of the following is an oxidising agent in $2Mg+O_2\left(g\right)\to 2MgO\left(s\right)$

1. Mg
2. $O_2$
3. Both Mg and O
4. None of these