How many moles of $K_2Cr_2O_7$ can be reduced by $1 \ mol$ of $Sn^{2+}$?

Chlorine is used to purify drinking water. Excess of chlorine is harmful. The excess of chlorine is removed by treating with sulphur dioxide. Present a balanced equation for this redox change taking place in water.

What are $x, y$ and $z$ respectively in the following reaction?
$xFe^{2+}{_{\text{(aq)}}} + yH^{+}{_{\text{(aq)}}} + zCr_2O_7^{2-}{_{\text{(aq)}}} \rightarrow \frac{y}{2}H_2O_{\text{(l)}} + xFe^{3+}{_{\text{(aq)}}} + 2zCr^{3+}{_{\text{(aq)}}}$

The coefficients $x, y, p, q,$ and $r$ in the following balanced equation are respectively:
$xMnO_4^{2-}{_{\text{(aq)}}} + yH_2O_{\text{(l)}} \rightarrow pMnO_2{_{\text{(s)}}} + qMnO_4^{-}{_{\text{(aq)}}} + rOH^{-}{_{\text{(aq)}}}$

Assertion: Change in color of acidic solution of potassium dichromate by breath is used to test drunk drivers.
Reason: Change in color is due to the complexation of alcohol with potassium dichromate.

$KMnO_4$ reacts with ferrous sulphate according to the equation:
$MnO_4^- + 5Fe^{2+} + 8H^{+} \to Mn^{2+} + 5Fe^{3+} + 4H_2O$
Here,$10 \ mL$ of $0.1 \ M$ $KMnO_4$ is equivalent to: