Answer:
88.5 g/m is the molar mass for the gas
Explanation:
We need the Ideal Gases Law equation to solve this:
P . V = n . R . T
Pressure (P) = 10 Torr
We must convert to atm → 10 Torr / 760 Torr = 0.0131 atm
Volume (V) = 255 mL
We must convert to L → 255 mL / 1000 = 0.255 L
n = number of moles
moles = mass in g / molar mass
12.1 mg/ 1000 = 0.0121 g
T° = 25°C + 273K = 298K
R = 0.082 L.atm /mol.K
Let's replace the values
0.0131 atm . 0.255L = 0.0121 g / x . 0.082 L.atm /mol.K . 298K
(0.0131 atm . 0.255L) / (0.082 L.atm /mol.K . 298K) = 0.0121 g / x
1.367×10⁻⁴ /mol = 0.0121 g / x
x = 0.0121 g / 1.367×10⁻⁴ mol = 88.5 g/m
