JEE MAIN - Chemistry (2025 - 29th January Evening Shift - No. 5)
0.1 M solution of KI reacts with excess of $\mathrm{H}_2 \mathrm{SO}_4$ and $\mathrm{KIO}_3$ solutions. According to equation
$$ 5 \mathrm{I}^{-}+\mathrm{IO}_3^{-}+6 \mathrm{H}^{+} \rightarrow 3 \mathrm{I}_2+3 \mathrm{H}_2 \mathrm{O} $$
Identify the correct statements :
(A) 200 mL of KI solution reacts with 0.004 mol of $\mathrm{KIO}_3$
(B) 200 mL of KI solution reacts with 0.006 mol of $\mathrm{H}_2 \mathrm{SO}_4$
(C) 0.5 L of KI solution produced 0.005 mol of $\mathrm{I}_2$
(D) Equivalent weight of $\mathrm{KIO}_3$ is equal to ( $\frac{\text { Molecular weight }}{5}$ )
Choose the correct answer from the options given below :
Explanation
Molarity of KI = 0.1 M
$$5{I^ - } + IO_3^ - + 6{H^ + } \to 3{I_2} + 3{H_2}O$$ (balanced chemical equation)
$$5KI + KI{O_3} + 3{H_2}S{O_4} \to 3{I_2} + 3{K_2}S{O_4} + 3{H_2}O$$
(A) Volume given (KI) = 200 mL = 0.2 L
Molarity (KI) = 0.1 M or mol L$^{-1}$
The molarity formula is used here to calculate the number of moles of K.I.
Molarity, $$M = {{number\,of\,moles} \over {volume\,in\,L}}$$
So, number of moles = Molarity $\times$ Volume in L
For the given volume of KI,
number of moles = 0.1 mol L$^{-1}$ $\times$ 0.2 L
= 0.02 mol
The stoichiometric ratio between KI and KIO$_3$ is
$$KI:KI{O_3}$$
$${I^ - }:IO_3^ - $$
$$5:1$$
$$1:{1 \over 5}$$
For one mol $${I^ - },{1 \over 5}$$ mol $$IO_3^ - $$ is used.
So, for 0.2 mol I$^-$,
Moles of $$IO_3^ - = 0.02 \times {1 \over 5} = 0.004$$ mol
The statement (A) is correct.
(B) Volume given (KI) = 200 mL = 0.2 L
Molarity (KI) = 0.1 M
number of moles of KI (I$^-$) = Molarity $\times$ Volume (L)
$$ = 0.1\,mol\,{L^{ - 1}} \times 0.2\,L = 0.02\,mol$$
The stoichiometric ratio between KE and $${H_2}H{O_4}$$ is
$$KI:{H_2}H{O_4}$$
$$5:3$$
$$1:{3 \over 5}$$ {3 moles $${H_2}S{O_4}$$ can give 6H$^+$}
$${I^ - },{3 \over 5}$$
For one mol $${I^ - },{3 \over 5}$$ mol $${H_2}S{O_4}$$ is used.
So, for 0.02 mol I$^-$,
moles of $${H_2}S{O_4} = 0.02 \times {3 \over 5} = 0.012$$ mol
This statement is not correct.
(C) Volume gien (KI) = 0.5 L
Molarity (KI) = 0.1 M
Number of moles of KI = Molarity $\times$ Volume
$$ = 0.1\,mol\,{L^{ - 1}} \times 0.5\,L = 0.05\,mol$$
The stoichiometric ratio between I$^-$ and I$_2$ is
$$KI:{I_2}$$
$${I^ - }:{I_2}$$
$$5:3$$
$$1:{3 \over 5}$$
For 1 mol $${I^ - },{3 \over 5}$$ mol I$_2$ is produced.
So, for 0.05 mol, moles of $${I_2} = 0.05 \times {3 \over 5} = 0.03$$ mol
This statement is not correct.
(D) Equivalent weight of $$KI{O_3} = {{Molecular\,weight} \over 5}$$
This statement is correct.
Equivalent weight $$ = {{Molecular\,weight} \over {Valency\,factor\, \to number\,of\,electrons}}$$
Here, valency factor = 5
Each KIO$_3$ molecule gains 5 electrons in this vacation.
KIO$_3$ acts as the ordinating agent, gains electrons from the iodide ion in KI.
When KIO$_3$ is redued to I$_2$ each molecule gains 5 electrons. So, the valency factor is 5 and equivalent weight is lower than molecular weight.
This statement is correct.
Correct statements are A and D.
Comments (0)
