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121.
A compound of $$Xe$$ and $$F$$ is found to have $$53.5\% $$ of $$Xe.$$ What is oxidation number of $$Xe$$ in this compound ?
A
$$-4$$
B
$$0$$
C
$$+4$$
D
$$+6$$
Answer :
$$+6$$
$$\eqalign{
& Xe = 53.5\% \,\,\therefore \,\,F = 46.5\% \cr
& {\text{Relative number of atoms }}Xe \cr
& = \frac{{53.5}}{{131.2}} = 0.4\,{\text{and}}\,F = \frac{{46.5}}{{19}} = 2.4 \cr} $$
Simple ratio $$Xe = 1$$ and $$F = 6 ;$$ Molecular formula is $$Xe{F_6}$$
$$O.N$$ of $$Xe$$ is $$+6$$
122.
Which of the following is not a disproportionation reaction?
Disproportionation involves simultaneous oxidation and reduction of the same atom
in a molecule.
123.
The more positive the value of $${E^ \circ },$$ the greater is the tendency of the species to get reduced. Using the standard electrode potential of redox couples given below find out which of the following is the strongest oxidising agent.
$${E^ \circ }$$ values : $$\frac{{F{e^{3 + }}}}{{F{e^{2 + }}}} = + 0.77;\frac{{{I_{2\left( s \right)}}}}{{{I^ - }}} = + 0.54;$$ $$\frac{{C{u^{2 + }}}}{{Cu}} = + 0.34;\frac{{A{g^ + }}}{{Ag}} = + 0.80\,V$$
A
$$F{e^{3 + }}$$
B
$${I_{2\left( s \right)}}$$
C
$$C{u^{2 + }}$$
D
$$A{g^ + }$$
Answer :
$$A{g^ + }$$
Strongest oxidising agent means it has greater tendency to get reduced. Thus, $$A{g^ + }$$ having more positive $${E^ \circ }$$ value, is the strongest oxidising agent.
124.
The $${E^ \circ }$$ values of redox complex of halogens are given. Based on these values mark the correct statement. $$E_{\frac{{{I_2}}}{{{I^ - }}}}^ \circ = + 0.54\,V,E_{\frac{{B{r_2}}}{{B{r^ - }}}}^ \circ = + 1.08\,V,$$ $$E_{\frac{{C{l_2}}}{{C{l^ - }}}}^ \circ = + 1.36\,V,$$
A
Chlorine can displace bromine and iodine from their salt solutions.
B
Chlorine can only displace iodine from its salt solution.
C
Bromine can displace chlorine from its salt solution.
D
Iodine can displace chlorine and bromine from their salt solutions.
Answer :
Chlorine can displace bromine and iodine from their salt solutions.
Since chlorine has higher reduction potential than bromine and iodine so it can displace them from their salt solutions.
$$\eqalign{
& 2NaI + C{l_2} \to 2NaCl + {I_2} \cr
& 2NaBr + C{l_2} \to 2NaCl + B{r_2} \cr} $$
125.
The number of moles of $${K_2}C{r_2}{O_7}$$ reduced by one mole of $$S{n^{2 + }}$$ ions is
126.
In which of the following compounds, an element exhibits two different oxidation states?
A
$$N{H_2}OH$$
B
$$N{H_4}N{O_3}$$
C
$${N_2}{H_4}$$
D
$${N_3}H$$
Answer :
$$N{H_4}N{O_3}$$
In $$N{H_4}N{O_3},$$ oxidation state of $$N$$ in $$NH_4^ + $$ is - 3 while in $$NO_3^ - $$ is + 5.
127.
What will be the balanced equation in acidic medium for the given reaction?
$$C{r_2}O_{7\left( {aq} \right)}^{2 - } + S{O_{2\left( g \right)}} \to Cr_{\left( {aq} \right)}^{3 + } + SO_{4\left( {aq} \right)}^{2 - }$$
128.
Given
$$\eqalign{
& F{e^{3 + }}\left( {aq} \right) + {e^ - } \to F{e^{2 + }}\left( {aq} \right);{E^ \circ } = + 0.77\,V \cr
& A{l^{3 + }}\left( {aq} \right) + 3{e^ - } \to Al\left( s \right);{E^ \circ } = - 1.66\,V \cr
& B{r_2}\left( {aq} \right) + 2{e^ - } \to 2B{r^ - }\left( {aq} \right);{E^ \circ } = + 1.09\,V \cr} $$
Considering the electrode potentials, which of the following represents the correct order of reducing power?
A
$$F{e^{2 + }} < Al < B{r^ - }$$
B
$$B{r^ - } < F{e^{2 + }} < Al$$
C
$$Al < B{r^ - } < F{e^{2 + }}$$
D
$$Al < F{e^{2 + }} < B{r^ - }$$
Answer :
$$Al < F{e^{2 + }} < B{r^ - }$$
Reducing character decreases down the series. Hence the correct order is $$Al < F{e^{2 + }} < B{r^ - }$$
129.
Which one of the following cannot function as an oxidising agent ?
A
$${I^ - }$$
B
$$S\left( s \right)$$
C
$$NO_3^ - \left( {aq} \right)$$
D
$$C{r_2}O_7^{2 - }$$
Answer :
$${I^ - }$$
If an electronegative element is in its lowest possible oxidation state in a compound or in free state. It can function as a powerful reducing agent. e.g. $${I^ - }$$
130.
Which of the following are the common oxidising agents used in redox titrations?
A
$${K_2}C{r_2}{O_7},KMn{O_4},$$ Iodine
B
$$FeS{O_4},KMn{O_4},$$ Sodium thiosulphate
C
Oxalic acid, $$KMn{O_4},CuS{O_4}$$
D
Mohr's salt, $$KI,$$ Sodium sulphate
Answer :
$${K_2}C{r_2}{O_7},KMn{O_4},$$ Iodine
$${K_2}C{r_2}{O_7},KMn{O_4}$$ and iodine are used as oxidising agents for redox titrations.