Question

How many grams of H2 do you need to get - 155 kj

Answer 1

$H_2+\frac{1}{2}O_2 \to H_2O$

$∆H=-241.8kJ$

So:

$241.8kJ$ are produced from $1 mole = 2g H_2$

So $-155kJ$ produced from

$\frac{2}{241.8}×155=1.282grams$