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JEE Mains | PYQ

Iron \( (\mathrm{III}) \) catalyses the reaction between iodide and persulphate ions, in which?
A. \( \mathrm{Fe^{3+}} \) oxidises the iodide ion
B. \( \mathrm{Fe^{3+}} \) oxidises the persulphate ion
C. \( \mathrm{Fe^{2+}} \) reduces the iodide ion
D. \( \mathrm{Fe^{2+}} \) reduces the persulphate ion
Choose the most appropriate answer from the options given below:

If \( 50 \, \text{mL} \) of \( 0.5 \, \text{M} \) oxalic acid is required to neutralise \( 25 \, \text{mL} \) of NaOH solution, the amount of NaOH in \( 50 \, \text{mL} \) of given NaOH solution is ___ \( \text{g} \).

Given below are two statements:
Statement (I) : Potassium hydrogen phthalate is primary standard for standardisation of sodium hydroxide solution.
Statement (II) : In this titration phenolphthalein can be used as indicator.
In the light of the above statements, choose the most appropriate answer from the options given below:

Which of the following cannot function as an oxidizing agent?

In acidic medium, \( \mathrm{K_2Cr_2O_7} \) shows oxidising action as represented in the half reaction: 
$Cr_2O_7^{2-} + XH^+ + Ye^{\ominus} \rightarrow 2A + ZH_2O$
\( X \), \( Y \), \( Z \) and \( A \) respectively are:

Total number of species from the following which can undergo disproportionation reaction is _______.
\( \mathrm{H_2O_2,\ ClO_3^{-},\ P_4,\ Cl_2,\ Ag,\ Cu^{+1},\ F_2,\ NO_2,\ K^{+}} \)

From the given list, the number of compounds with +4 oxidation state of Sulphur is ___________ .
$\text{SO}_3$, $\text{H}_2\text{SO}_3$, $\text{SOCl}_2$, $\text{SF}_4$, $\text{BaSO}_4$, $\text{H}_2\text{S}_2\text{O}_7$

The lowest oxidation number of an atom in a compound \( \mathrm{A_2B} \) is \( -2 \). The number of electrons in its valence shell is _______.

Which of the following reactions are disproportionation reactions?
(A) \( \text{Cu}^+ \rightarrow \text{Cu}^{2+} + \text{Cu} \)
(B) \( 3\text{MnO}_4^{2-} + 4\text{H}^+ \rightarrow 2\text{MnO}_4^- + \text{MnO}_2 + 2\text{H}_2\text{O} \)
(C) \( 2\text{KMnO}_4 \rightarrow \text{K}_2\text{MnO}_4 + \text{MnO}_2 + \text{O}_2 \)
(D) \( 2\text{MnO}_4^- + 3\text{Mn}^{2+} + 2\text{H}_2\text{O} \rightarrow 5\text{MnO}_2 + 4\text{H}^+ \)
Choose the correct answer from the options given below:

Only \( 2 \, \mathrm{mL} \) of \( \mathrm{KMnO}_4 \) solution of unknown molarity is required to reach the end point of a titration of \( 20 \, \mathrm{mL} \) of oxalic acid \( (2 \, \mathrm{M}) \) in acidic medium. The molarity of \( \mathrm{KMnO}_4 \) solution should be \( \_\_\_\_\_\_ \, \mathrm{M} \).

Chlorine undergoes disproportionation in alkaline medium as shown below:
\( a\mathrm{Cl_2}(g) + b\mathrm{OH^-}(aq) \rightarrow c\mathrm{ClO^-}(aq) + d\mathrm{Cl^-}(aq) + e\mathrm{H_2O}(l) \)
The values of \( a \), \( b \), \( c \) and \( d \) in a balanced redox reaction are respectively:

Thiosulphate reacts differently with iodine and bromine in the reactions given below:
\( 2\mathrm{S_2O_3}^{2-} + \mathrm{I_2} \rightarrow \mathrm{S_4O_6}^{2-} + 2\mathrm{I^-} \)
\( \mathrm{S_2O_3}^{2-} + 5\mathrm{Br_2} + 5\mathrm{H_2O} \rightarrow 2\mathrm{SO_4}^{2-} + 4\mathrm{Br^-} + 10\mathrm{H^+} \)
Which of the following statement justifies the above dual behaviour of thiosulphate?

$2MnO_4^- + bI^- + cH_2O \rightarrow x I_2 + yMnO_2 + z\overline{O}H$
If the above equation is balanced with integer coefficients, the value of \( z \) is ________.