The equation of the perfect gas is
PV=nRTPV=nRT
PP is the pressure that we want to calculate, VV is the volume in "m"^3m3, nn are the mols, RR is the constant of perfect gas 8.314472 ("m"^3"Pa")/("mol" "K")8.314472m3PamolK, TT is the temperature in "K"K.
First of all we need to transform our quantity in the proper units:
V=11.2 "L"=11.2*10^-3 "m"^3V=11.2L=11.2⋅10−3m3
T=30^\circ"C"=30+273.15 "K"=303.15"K"T=30∘C=30+273.15K=303.15K.
The pressure is
P=(nRT)/V=(0.25 cancel"mol"*8.314472 (cancel("m"^3)"Pa")/(cancel"mol" cancel"K")*303.15cancel"K")/(11.2*10^-3 cancel("m"^3))
=(0.25* 8.314472*303.15)/(11.2)*10^3"Pa"
=56261.88" Pa", or, if we want in a more familiar unit, we can convert it in atm using the conversion 1"atm"=101325"Pa" then
56261.88" Pa"= 56261.88/101325" atm"
=0.555" atm".