Question

number of H ^- ions in 5.44 g SrH₂

Answer 1

The molar mass of SrH₂ is 89.64 g/mol, and there are 2 moles of H^- ions per 1 mole of SrH₂. Therefore,

$Number\ of\ H^-=5.44\ g(SrH_2)\times\frac{1\ mol(SrH_2)}{89.64\ g(SrH_2)}\times\frac{2\ mol(H^-)}{1\ mol(SrH_2)}\times\frac{6.022\times10^{23}\ ions(H^-)}{1\ mol(H^-)}=7.31\times10^{22}\ ions$

Answer: $7.31\times10^{22}$