We can use the ideal gas law to calculate the mass of helium:
$$PV = nRT$$
where:
- P is the pressure in atm
- V is the volume in liters
- n is the amount of substance in moles
- R is the ideal gas constant (0.08206 L * atm / mol * K)
- T is the temperature in Kelvin
Rearranging the equation to solve for n, we get:
$$n = PV/RT$$
Substituting the given values:
$$n = (1 atm * 43.7 L) / (0.08206 L * atm / mol * K * 273.15 K)$$
$$n = 1.923 mol$$
Finally, we can calculate the mass of helium by multiplying the amount of substance by the molar mass:
$$mass = n * molar mass$$
$$mass = 1.923 mol * 4.0026 g/mol$$
$$mass = 7.71 g$$
Therefore, the mass of 43.7 L helium at STP is 7.71 g.
