Determining Electrons (X) for Iodide Oxidation
We need to find the number of electrons (X) involved when iodide ion ($\text{I}^-$) is oxidized to iodine ($\text{I}_2$) by acidified $\text{K}_2\text{Cr}_2\text{O}_7$.
The oxidation half-reaction is: $2\text{I}^- \rightarrow \text{I}_2 + 2e^-$
However, the question asks for electrons involved *during the oxidation... by acidified $\text{K}_2\text{Cr}_2\text{O}_7$*. This implies balancing the electrons transferred in the oxidation half-reaction against the reduction of the oxidizing agent, $\text{K}_2\text{Cr}_2\text{O}_7$.
The reduction half-reaction for dichromate ($\text{Cr}_2\text{O}_7^{2-}$) in acidic medium is: $\text{Cr}_2\text{O}_7^{2-} + 14\text{H}^+ + 6e^- \rightarrow 2\text{Cr}^{3+} + 7\text{H}_2\text{O}$ This reaction involves the gain of 6 electrons.
To balance the 6 electrons gained by dichromate, the oxidation of iodide must supply 6 electrons. The simple half-reaction $2\text{I}^- \rightarrow \text{I}_2 + 2e^-$ needs to be multiplied by 3 to provide 6 electrons: $3 \times (2\text{I}^- \rightarrow \text{I}_2 + 2e^-)$ $6\text{I}^- \rightarrow 3\text{I}_2 + 6e^-$ Therefore, the number of electrons involved in the oxidation of iodide in this context is X = 6.
Determining Electrons (Y) for Sulfide Oxidation
We need to find the number of electrons (Y) involved when sulfide ion ($\text{S}^{2-}$) is oxidized to elemental sulfur (S) by acidified $\text{K}_2\text{Cr}_2\text{O}_7$.
The oxidation half-reaction is: $\text{S}^{2-} \rightarrow \text{S} + 2e^-$
Similar to the iodide case, we need to consider the electron transfer relative to the reduction of dichromate (which involves 6 electrons).
To balance the 6 electrons gained by dichromate, the oxidation of sulfide must supply 6 electrons. The half-reaction $\text{S}^{2-} \rightarrow \text{S} + 2e^-$ needs to be multiplied by 3 to provide 6 electrons: $3 \times (\text{S}^{2-} \rightarrow \text{S} + 2e^-)$ $3\text{S}^{2-} \rightarrow 3\text{S} + 6e^-$ Therefore, the number of electrons involved in the oxidation of sulfide in this context is Y = 6.
Calculating X + Y
We found that X = 6 and Y = 6.
The total number of electrons is the sum: $ \text{X} + \text{Y} = 6 + 6 = 12 $
Similar Questions
- The cycloalkene (X) on bromination consumes one mole of bromine per mole of (X) and gives the product (Y) in which C:Br ratio is 3:1. The percentage of bromine in the product (Y) is _________%. (Nearest integer)
(Given : molar mass in $\text{g mol}^{-1} \text{ H} : 1, \text{ C} : 12, \text{ O} : 16, \text{ Br} : 80$) - Dissociation of a gas $\text{A}_2$ takes place according to the following chemical reaction. At equilibrium, the total pressure is $1 \text{ bar}$ at $300\text{K}$.
$\text{A}_2\text{(g)} \rightleftharpoons 2\text{A(g)}$
The standard Gibbs energy of formation of the involved substances has been provided below:Substance $\Delta G_f^\circ / \text{kJ mol}^{-1}$ $\text{A}_2$ -100.00 A -50.832
The degree of dissociation of $\text{A}_2\text{(g)}$ is given by $(x \times 10^{-2})^{1/2}$ where $x =$ _________. (Nearest integer).
$[\text{Given: } \text{R} = 8 \text{ J mol}^{-1}\text{ K}^{-1}, \log 2 = 0.3010, \log 3 = 0.48]$
Assume degree of dissociation is not negligible. - Which of the following mixture gives a buffer solution with pH = 9.25 ?
Given : $\text{pK}_b (\text{NH}_4\text{OH}) = 4.75$ Identify the correct statements :
A. Hydrated salts can be used as primary standard.
B. Primary standard should not undergo any reaction with air.
C. Reactions of primary standard with another substance should be instantaneous and stoichiometric.
D. Primary standard should not be soluble in water.
E. Primary standard should have low relative molar mass.
Choose the correct answer from the options given below :- Consider $\text{A} \xrightarrow{k_1} \text{B}$ and $\text{C} \xrightarrow{k_2} \text{D}$ are two reactions. If the rate constant ($k_1$) of the $\text{A} \longrightarrow \text{B}$ reaction can be expressed by the following equation $\log_{10} k = 14.34 - \frac{1.5 \times 10^4}{T/K}$ and activation energy of $\text{C} \longrightarrow \text{D}$ reaction ($\text{Ea}_2$) is $\frac{1}{5}$th of the $\text{A} \longrightarrow \text{B}$ reaction ($\text{Ea}_1$), then the value of ($\text{Ea}_2$) is _________ $\text{kJ mol}^{-1}$. (Nearest Integer)
- Consider the following electrochemical cell :
$\text{Pt} \mid \text{O}_2\text{(g)}(1\text{bar}) \mid \text{HCl(aq)} \parallel \text{M}^{2+}\text{(aq, 1.0 M)} \mid \text{M(s)}$
The pH above which, oxygen gas would start to evolve at anode is _________ (nearest integer).
Given :
$\begin{bmatrix} \text{E}^\circ_{\text{M}^{2+}/\text{M}} = 0.994 \text{ V} \\ \text{E}^\circ_{\text{O}_2/\text{H}_2\text{O}} = 1.23 \text{ V} \end{bmatrix} \text{standard reduction potential}$
and $\frac{\text{RT}}{\text{F}} (2.303) = 0.059 \text{ V}$ at the given condition - At $27^\circ\text{C}$ in presence of a catalyst, activation energy of a reaction is lowered by $10 \text{ kJ mol}^{-1}$. The logarithm of ratio of $\frac{k(\text{catalysed})}{k(\text{uncatalysed})}$ is....
(Consider that the frequency factor for both the reactions is same) - Consider two Group IV metal ions $\text{X}^{2+}$ and $\text{Y}^{2+}$.
A solution containing 0.01 M $\text{X}^{2+}$ and 0.01 M $\text{Y}^{2+}$ is saturated with $\text{H}_2\text{S}$. The pH at which the metal sulphide YS will form as a precipitate is ______. (Nearest integer)
(Given: $\text{K}_{sp}(\text{XS}) = 1 \times 10^{-22}$ at $25^\circ\text{C}$, $\text{K}_{sp}(\text{YS}) = 4 \times 10^{-16}$ at $25^\circ\text{C}$, $[\text{H}_2\text{S}] = 0.1\text{M}$ in solution, $\text{K}_{a1} \times \text{K}_{a2}(\text{H}_2\text{S}) = 1.0 \times 10^{-21}$, $\log 2 = 0.30$, $\log 3 = 0.48$, $\log 5 = 0.70$) - Electricity is passed through an acidic solution of $\text{Cu}^{2+}$ till all the $\text{Cu}^{2+}$ was exhausted, leading to the deposition of 300 mg of Cu metal. However, a current of 600 mA was continued to pass through the same solution for another 28 minutes by keeping the total volume of the solution fixed at 200 mL. The total volume of oxygen evolved at STP during the entire process is ______ mL. (Nearest integer)
[Given:
$\text{Cu}^{2+}\text{(aq)} + 2\text{e}^- \rightarrow \text{Cu(s)} \quad \text{E}^\circ_{\text{red}} = +0.34 \text{ V}$
$\text{O}_2\text{(g)} + 4\text{H}^+ + 4\text{e}^- \rightarrow 2\text{H}_2\text{O} \quad \text{E}^\circ_{\text{red}} = +1.23 \text{ V}$
Molar mass of Cu = $63.54 \text{ g mol}^{-1}$
Molar mass of $\text{O}_2$ = $32 \text{ g mol}^{-1}$
Faraday Constant = $96500 \text{ C mol}^{-1}$
Molar volume at STP = 22.4 L] - Two liquids A and B form an ideal solution at temperature T K. At T K, the vapour pressures of pure A and B are 55 and $15 \text{ kN m}^{-2}$ respectively. What is the mole fraction of A in solution of A and B in equilibrium with a vapour in which the mole fraction of A is 0.8?
Important Questions from Physical Chemistry
- The cycloalkene (X) on bromination consumes one mole of bromine per mole of (X) and gives the product (Y) in which C:Br ratio is 3:1. The percentage of bromine in the product (Y) is _________%. (Nearest integer)
(Given : molar mass in $\text{g mol}^{-1} \text{ H} : 1, \text{ C} : 12, \text{ O} : 16, \text{ Br} : 80$) - Dissociation of a gas $\text{A}_2$ takes place according to the following chemical reaction. At equilibrium, the total pressure is $1 \text{ bar}$ at $300\text{K}$.
$\text{A}_2\text{(g)} \rightleftharpoons 2\text{A(g)}$
The standard Gibbs energy of formation of the involved substances has been provided below:Substance $\Delta G_f^\circ / \text{kJ mol}^{-1}$ $\text{A}_2$ -100.00 A -50.832
The degree of dissociation of $\text{A}_2\text{(g)}$ is given by $(x \times 10^{-2})^{1/2}$ where $x =$ _________. (Nearest integer).
$[\text{Given: } \text{R} = 8 \text{ J mol}^{-1}\text{ K}^{-1}, \log 2 = 0.3010, \log 3 = 0.48]$
Assume degree of dissociation is not negligible. - Which of the following mixture gives a buffer solution with pH = 9.25 ?
Given : $\text{pK}_b (\text{NH}_4\text{OH}) = 4.75$ Identify the correct statements :
A. Hydrated salts can be used as primary standard.
B. Primary standard should not undergo any reaction with air.
C. Reactions of primary standard with another substance should be instantaneous and stoichiometric.
D. Primary standard should not be soluble in water.
E. Primary standard should have low relative molar mass.
Choose the correct answer from the options given below :- Consider $\text{A} \xrightarrow{k_1} \text{B}$ and $\text{C} \xrightarrow{k_2} \text{D}$ are two reactions. If the rate constant ($k_1$) of the $\text{A} \longrightarrow \text{B}$ reaction can be expressed by the following equation $\log_{10} k = 14.34 - \frac{1.5 \times 10^4}{T/K}$ and activation energy of $\text{C} \longrightarrow \text{D}$ reaction ($\text{Ea}_2$) is $\frac{1}{5}$th of the $\text{A} \longrightarrow \text{B}$ reaction ($\text{Ea}_1$), then the value of ($\text{Ea}_2$) is _________ $\text{kJ mol}^{-1}$. (Nearest Integer)
