The coagulating power of electrolytes having ions $Na^{+} ,Al^{3+}$ and $Ba^{2+}$ for arsenic sulphide sol increases in the order :

Question

$\begin{array}{1 1} (1) Al^{3+} < Ba^{2+} < Na^{+} \\ (2) Na{+} < Ba^{2+} < Al^{3+} \\ (3) Ba^{2+} < Na^{+} < Al^{3+} \\(4) Al^{3+} < Na^{+} < Ba^{+} \end {array}$