$.$ A tank with a capacity of $3\mathrm{.}64$ L has Helium gas, pumped into it$.(1\mathrm{.}5$ Mark$)$

$1)$ How many moles of gas are contained in the tank at $0\backslash$deg C and $14\mathrm{.}7$ psi?

$2)$ How many molecules are there in the tank in part $1?$

$3)$ If hydrogen, a diatomic gas, had been pumped in instead, how many molecules would there be in the tank?