At standard temperature and pressure (STP), which is defined as 0 degrees Celsius (273.15 Kelvin) and 1 atmosphere (101.325 kPa), the volume of 1 mole of methane gas (CH4) can be calculated using the ideal gas law:

PV = nRT

Where:

P = pressure = 1 atm

V = volume (unknown)

n = number of moles = 1 mole

R = ideal gas constant = 0.08206 L*atm/mol*K

T = temperature = 273.15 K

Solving for V, we get:

V = nRT/P

V = (1 mole) * (0.08206 L*atm/mol*K) * (273.15 K) / (1 atm)

V = 22.414 L

Therefore, the volume of 1 mole of methane gas at STP is 22.414 liters.