# Which of the following fumes in moist air?

$\begin{array}{1 1}(a)\;BeCl_2&(b)\;CaCl_2\\(c)\;SrCl_2&(d)\;BaCl_2\end{array}$

$BeCl_2$
Beryllium chloride is a salt of strong acid and weak base. It undergoes hydrolysis in the presence of moisture present in air to form fumes of HCl gas. Therefore, it fumes in moist air.
$BeCl_2+2H_2O\rightarrow Be(OH)_2+2HCl$
Hence (a) is the correct answer.
edited Nov 25, 2017