For neon, determine the moles and mass contained in a 29.9−L volume at a pressure of 481.1 torr at a temperature of 300.0 K.

.7689 mol

15.516 g

Explanation:

Use the Ideal Gas Law, PV = nRT.

Make sure to use the correct ideal gas constant R. You can either put R in torr, or you can change the pressure to atm. I've just used the torr ideal gas constant.

481.1 torr * 29.9 L = n 62.364 LTorr/molK * 300 K

14384.89 = 18709.2n

n = .7689 mol

The molar mass of neon (remember that neon gas = Ne, it's not diatomic) is 20.18 g/mol from the periodic table.

.7689 mol * 20.18 g/mol = 15.516 g

your answer is a. the enthalpy of formation for a pure element in its standard state is always positive.

i belive it is water