Answer
See the answer below.
Work Step by Step
a) The number of moles of $NaBH_4$ is:
$0.136\ g\div 37.83\ g/mol=3.595×10^{-3}\ mol$
From stoichiometry, it follows:
$1.797×10^{-3}\ mol$ diborane.
Using the ideal gas law and plugging in the known values, it follows:
$P=nRT/V$
$P=0.016\ atm$
b) From Dalton's law: $P_{H_2}=2×P_{B_2H_4}$, so the total pressure is: $P=0.048\ atm$
