When $KMnO_4$ solution is titrated with a solution containing $Fe^{2+}$ ions,the indicator used in this titration is

In which of the following reactions does the element sulfur get reduced?

Identify the type of the following chemical reaction:
$CuSO_4 + 2KI \longrightarrow CuI \downarrow + \frac{1}{2} I_2 + K_2SO_4$

One litre of $0.15 \ M \ Na_2SO_3$ aqueous solution is mixed with $500 \ mL$ of $0.2 \ M \ K_2Cr_2O_7$ aqueous solution in acid medium. What is the concentration (in $mol \ L^{-1}$) of unreacted $K_2Cr_2O_7$ in the resultant solution?

Assign $A, B, C, D$ from the given type of reaction.
$Ba(NO_3)_2 + Na_2SO_4 \longrightarrow BaSO_4 \downarrow + 2NaNO_3$

If salt $Q$ undergoes a redox reaction with $H_2S$ in an acidic medium,then which of the following species cannot be a possible product?