$100 \, mL$ of a sample containing calcium oxalate $[CaC_2O_4]$ is dissolved in an acidic solution. It required $20 \, mL$ of $1 \, M \, KMnO_4$ for complete oxidation. Find the mass of $Ca^{2+}$ ions (in grams) present in the sample. [Atomic mass of $Ca = 40$]

When mercury $(II)$ chloride is treated with excess of $SnCl_2$,the products obtained are

$A$ solution of $10 \ mL$ of $\frac{M}{10} \ FeSO_4$ was titrated with $KMnO_4$ solution in an acidic medium. The amount of $KMnO_4$ used will be:

To an acidified dichromate solution,a pinch of $Na_2O_2$ is added and shaken. What is observed?

Which of the following act as an oxidising as well as a reducing agent?

Oxidising power of chlorine in aqueous solution can be determined by the parameters indicated below:
$\frac{1}{2} Cl_{2(g)}$ $\xrightarrow{\frac{1}{2} \Delta_{diss} H^{\Theta}} Cl_{(g)}$ $\xrightarrow{\Delta_{eg} H^{\Theta}} Cl^{-}_{(g)}$ $\xrightarrow{\Delta_{Hyd} H^{\Theta}} Cl^{-}_{(aq)}$
(using the data,$\Delta_{diss} H_{Cl_2}^{\Theta} = 240 \ kJ \ mol^{-1}$,$\Delta_{eg} H_{Cl}^{\Theta} = -349 \ kJ \ mol^{-1}$,$\Delta_{Hyd} H_{Cl}^{\Theta} = -381 \ kJ \ mol^{-1}$) will be ............. $kJ \ mol^{-1}$.