Answer: 14.7 atm
Step-by-step explanation:
Using the ideal gas law also called the general gas equation ;
PV = nRT
Where,
P = pressure
V = Volume
n = amount of substance
R = ideal gas constant
T = temperature
For the He sample;
V = 2.5 L
n = 1.5 mol
R = 8.314 J/mol/K or 0.0821 L atm/mol/K
T =?
T = PV/nR
T = 14.7*2.5/(1.5*0.0821)
T = 298.42K
For the H2 sample, since both are under the same condition :
P = nRT/V
P = (1.5*0.0821*298.42) รท 2.5
P = 14.7 atm.