Oxidation and Reduction

Q.

Find the oxidation number of$\mathrm{Cr}$ in ${\mathrm{K}}_2{\mathrm{Cr}}_2{\mathrm{O}}_7$.

Q. Why is $C{r}^{2+}$ reducing and $M{n}^{3+}$ oxidising when both have $d^4$ configuration?

Q.

Name the compound that gets oxidised in the following reaction: $4\mathrm{Na}+{\mathrm{O}}_2\to 2{\mathrm{Na}}_2\mathrm{O}$

Q. The specific conductance of $0.01M$ solution of acetic acid was found to be $0.0163S{m}^{-1}$ at $25°C$. Calculate the degree of dissociation of the acid. Molar conductance of acetic acid at infinite dilution is $390.7\times {10}^{-4}S{m}^{2}mo{l}^{-1}$ at $25°C$.

1. 0.0632
2. 0.0472
3. 0.0823
4. 0.0984

Q.

$\underset{\mathrm{lead}\mathrm{oxide}}{2\mathrm{PbO}\left(\mathrm{s}\right)}+\underset{\mathrm{Carbon}}{\mathrm{C}\left(\mathrm{s}\right)}\to \underset{\mathrm{Lead}}{2\mathrm{Pb}\left(\mathrm{s}\right)}+\underset{\mathrm{Carbon}\mathrm{dioxide}}{{\mathrm{CO}}_2\left(\mathrm{g}\right)}$

Name the oxidized substance, reduced substance, reducing agent, and oxidizing agent in this reaction.

Q. Primary alkyl halide $C_4{H}_{9}Br$ $\left(a\right)$ reacted with alcoholic $KOH$ to give compound $\left(b\right)$. Compound $\left(b\right)$ is reacted with $HBr$ to give $\left(c\right)$ which is an isomer of $\left(a\right)$. When $\left(a\right)$ is reacted with sodium metal it gives compound $\left(d\right)$, $C_8{H}_{18}$ which is different from the compound formed when $n$-butyl bromide is reacted with sodium. Give the structural formula of $\left(a\right)$ and write the equations for all the reactions.

Q.

What happen when copper chloride reacts with an aqueous solution of sodium hydroxide? State the color of the precipitate formed.

Q.

The chlorobenzene can be converted into benzene by reduction with nascent hydrogen produced by an alloy(metallic) in the presence of alkali, the metallic alloy used is

1. Cd-Al

2. Ni-Cd

3. Hg-Cd

4. Ni-Al

Q. The chemical nature of hydrogen peroxide is:

1. Reducing agent in basic medium, but not in acidic medium.
2. Oxidising and reducing agent in acidic medium, but not in basic medium.
3. Oxidising agent in acidic medium, but not in basic medium.
4. Oxidising and reducing agent in both acidic and basic medium.

Q.

The oxidation number of an element in a compound is evaluated on the basis of certain rules. Which of the following rules is not correct in this respect?

1. The algebraic sum of all the oxidation numbers in a compound is zero.

2. The oxidation number of hydrogen is always $+1$

3. In all its compounds, the oxidation number of fluorine is $-1.$

4. An element in the free or the uncombined state bears oxidation number zero.

Q. Which of the following is most powerful oxidizing agent

1. 
2. 
3. 
4. 

Q. Identify the redox reactions out of the following reactions and identify the oxidizing and reducing agents in them.

A) $3HCl\left(aq\right)+HN{O}_3\left(aq\right)\to C{l}_2\left(g\right)+NOCl\left(g\right)+2H_{2}O\left(l\right)$

B) $HgCl2\left(aq\right)+2KI\left(aq\right)\to HgI2\left(s\right)+2KCl\left(aq\right)$

C) $F{e}_2{O}_3\left(s\right)+3CO\left(g\right)\Delta \to 2Fe\left(s\right)+3C{O}_2\left(g\right)$

D) $PCl3\left(l\right)+3H2O\left(l\right)\to 3HCl\left(aq\right)+H3PO3\left(aq\right)$

E) $4NH3+3O2\left(g\right)\to 2N2\left(g\right)+6H2O\left(g\right)$

Q. Which one of the following complexes is violet in colour ?

1. $F{e}_4\left[Fe\right(CN{)}_6{]}_3.H_{2}O$
2. $\left[Fe\right(CN{)}_6{]}^{4-}$
3. $\left[Fe\right(CN{)}_{5}NOS{]}^{4-}$
4. $\left[Fe\right(SCN{)}_6{]}^{4-}$

Q. Standard reduction potentials of the half reactions are given below
$F_2\left(g\right)+2e^{-}\to 2F^{-}\left(aq\right);E^0=+2.85V$
$C{l}_2\left(g\right)+2e^{-}\to 2C{l}^{-}\left(aq\right);E^0=+1.36V$
$B{r}_2\left(l\right)+2e^{-}\to 2B{r}^{-}\left(aq\right);E^0=+1.06V$
$I_2\left(s\right)+2e^{-}\to 2I^{-}\left(aq\right);E^0=+0.53V$

The strongest oxidising and reducing agents respectively are:

1. $B{r}_2$ and $C{l}^{-}$
2. $C{l}_2$ and $B{r}^{-}$
3. $F_2$ and $I^{-}$
4. $C{l}_2$ and $I_2$

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

Q.

Identify the correct statement $\left(s\right)$ in relation to the following reaction:

$Zn+2HCl\to ZnC{l}_2+H_2$

1. Zinc is acting as a reductant

2. Zinc is acting as an oxidant

3. Chlorine is acting as a reductant

4. Hydrogen ion is acting as an oxidant

Q. Justify that the reaction:

$2Na\left(s\right)+H_2\left(g\right)\to 2NaH\left(s\right)$ is a redox change.

Q.

Describe what would you observe at the anode and the cathode during electrolysis of Copper chloride (II) using platinum cathode and carbon anode. Write ionic equations for the reactions at the anode and the cathode.

Q. Sample of 2, 3-dibromo-3-methylpentane is heated with zinc dust. The resulting product is isolated and heated with HI in the presence of phosphorus. Indicate which is the structure that represent the final organic product formed in the reaction

1. 
2. 
3. 
4. 

Q. The correct order of following 3d metal oxides, according to their oxidation number is:
(a) $Cr{O}_3$
(b) $F{e}_2{O}_3$
(c) $Mn{O}_2$
(d) $V_2{O}_5$
(e) $C{u}_{2}O$

1. $\left(a\right)>\left(d\right)>\left(c\right)>\left(b\right)>\left(e\right)$
2. $\left(d\right)>\left(a\right)>\left(b\right)>\left(c\right)>\left(e\right)$
3. $\left(a\right)>\left(c\right)>\left(d\right)>\left(b\right)>\left(e\right)$
4. $\left(c\right)>\left(a\right)>\left(d\right)>\left(e\right)>\left(b\right)$

Q. Which one of these ions absorbs energy from visible spectrum :- (1) [Cu(NH3)4]^+ (2) [Cu(NH3)4]^+2 (3) [Zn(H2O)6]^+2 (4) [Co(H2O)6]^+3

Q. When an oxide of manganese (A) is fused with 𝐾𝑂𝐻 in the presence of an oxidising agent and dissolved in water, it gives a dark green solution of compound (B). Compound (B) disproportionate in neutral or acidic solution to give purple compound (C). An alkaline solution of compound (C) oxidises potassium iodide solution to a compound (D) and compound (A) is also formed. Identify compounds A to D and explain the reactions involved.

Q.

Classify the following reactions-

(i) ${\mathrm{N}}_2+{\mathrm{O}}_2\to 2\mathrm{NO}-\mathrm{Heat}$

(ii) $2\mathrm{HgO}\to 2\mathrm{Hg}+{\mathrm{O}}_2$

(iii) ${\mathrm{Na}}_2{\mathrm{SO}}_4+{\mathrm{BaCl}}_2\to 2\mathrm{NaCl}+{\mathrm{BaSO}}_4$

(iv) ${\mathrm{CuSO}}_4\left(\mathrm{aq}\right)+\mathrm{Zn}\to {\mathrm{ZnSO}}_4\left(\mathrm{aq}\right)+\mathrm{Cu}$

(v) ${\mathrm{NH}}_3+\mathrm{HCl}\to {\mathrm{NH}}_4\mathrm{Cl}$

Q. Write one chemical reaction for the prepartion of $D_2{O}_2$

Q. In a galvanic cell, the electrons flow from

1. Anode to the cathode through the solution
2. Cathode to the anode through the solution
3. Anode to the cathode through the external circuit
4. Cathode to the anode through the external circuit

Q.

Name the type of reaction: AB + CD → AD + CB

Q.

How to convert oxidation potential to reduction potential?

Q.

A violet compound of manganese $\left(A\right)$ decomposes on heating to liberate oxygen and compounds $\left(B\right)$ and $\left(C\right)$ of manganese are formed. Compound $\left(C\right)$ reacts with $KOH$ in the presence of potassium nitrate to give compound $\left(B\right)$. On heating compound $\left(C\right)$ with conc. $H_{2}S{O}_4$ and $NaCl$, chlorine gas is liberated and a compound (D) of manganese along with other products is formed. Identify compounds A to D and also explain the reactions involved.

Q. At ${25}^{o}C$, the specific conductance of a saturated solution of $AgCl$ is $2.68\times {10}^{-4}S{m}^{-1}$ and that of water with which the solution was made is $0.86\times {10}^{-4}S{m}^{-1}$. If molar conductance at infinite dilution of $AgN{O}_3,HN{O}_3$ and $HCl$ are, respectively, $133.0\times {10}^{-4}$, $421\times {10}^{-4}$ and $426.0\times {10}^{-4}S{m}^{2}mo{l}^{-1}$.
Calculate the solubility of $AgCl$ in grams per $d{m}^3$ in water at the given temperature.

1. $0.5\times {10}^2$
2. $1.89\times {10}^{-3}$
3. $8.65\times {10}^{-3}$
4. $0.453$

Q.

Name the reducing agent, oxidising agent, substance oxidised and substance reduced in the following redox reaction:

$\mathrm{Cr}{}_2\mathrm{O}{}_3+2\mathrm{Al}\to 2\mathrm{Cr}+\mathrm{Al}{}_2\mathrm{O}{}_3$