what is the volume in liters of 4.2 moles methane gas, at 26degree C and 1.40 atm?

assuming that the gas is ideal, we use the formula for ideal gases:

PV = nRT
where
P = pressure (in atm)
V = volume (in L)
n = number of moles
R = gas constant (0.0821 L*atm/mol-K)
T = temperature (in Kelvin)
we first convert the 26 degrees Celsius to Kelvin:
26 + 273.15 = 299.15 K
substituting,
(1.40)(V) = (4.2)(0.0821)(299.15)
V = (4.2)(0.0821)(299.15)/(1.40)
V = 73.68 L

hope this helps~ :)