A sample of gas occupies 2.5 liters of space. How many moles of gas are there if its pressure is 1.2 atm and temperature is 25 C.

Moles of gas = 0.123

In general, the gas equation can be written  

where  

P = pressure, atm , N/m²

V = volume, liter  

n = number of moles  

R = gas constant = 0.082 l.atm / mol K (P= atm, v= liter),or 8,314 J/mol K (P=Pa or N/m2, v= m³)

T = temperature, Kelvin  

Volume(V) =2.5 L

Pressure(P) = 1.2 atm

Temperature(T) = 25 + 273=298 K

"standard molar enthalpy:

h2o ( liquid water ) : - 285.8 kj/mole

h2o ( water vapor ) : - 241.8 kj / mole.

δhrxn = - 241. 8 - ( - 285.8 )= -241.8 + 285.8 = 44.0

answer: 44.0 kj"