One of relatively few reactions that takes place directly between two solids at room temperature is

$Ba(OH{)}_2*8H_{2}O(s)+N{H}_{4}SCN(s)Ba(SCN{)}_2(s)+H_{2}O(l)+N{H}_3(g)$

In this equation, the $8H_{2}O$ in $Ba(OH{)}_2*8H_{2}O$ indicates the presence of eight water molecules. This compound is called barium hydroxide

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a$.$ Balance the equation.

$($Use the lowest possible coefficients for the reaction.$)$

$Ba(OH{)}_2*8H_{2}O(s)+N{H}_{4}SCN(s)$

$Ba(SCN{)}_2(s)+,H_{2}O(l)+,N{H}_3(g)$

b$.$ What mass of ammonium thiocyanate $(N{H}_{4}SCN)$ must be used if it is to react completely with $7\mathrm{.}3g$ barium hydroxide octahydrate?

Mass $=,g$