Answer
Please see the work below.
Work Step by Step
We know that
$PV=nRT$
This can be rearranged as:
$n=\frac{PV}{RT}$
We plug in the known values to obtain:
$n=\frac{97970\times 0.0041}{8.31\times 285}=0.17651molH_2$
The given reaction is :
$LiH+H_2O\rightarrow LiOH+H_2O$
moles ratio $LiH:H_2$=1:1
$moles \space of LiH=0.17651moles $
$Mass\space of \space LiH=moles\times molar\space mass$
$Mass\space of \space LiH=0.17651\times 7.9491=1.40g$
