Answer:
78.2 g/mol
Step-by-step explanation:
We can use the Ideal Gas Law to solve this problem:
pV = nRT
Since n = m/M, the equation becomes
pV = (m/M)RT Multiply each side by M
pVM = mRT Divide each side by pV
M = (mRT)/(pV)
Data:
ρ = 2.50 g/L
R = 0.082 16 L·atm·K⁻¹mol⁻¹
T =98 °C
p = 740 mmHg
Calculation:
(a) Convert temperature to kelvins
T = (98 + 273.15) = 371.15 K
(b) Convert pressure to atmospheres
p = 740 × 1/760 =0.9737 atm
(c) Calculate the molar mass
Assume V = 1 L.
Then m = 2.50 g
M = (2.50 × 0.082 06 × 371.15)/(0.9737 × 1)
= 76.14/0.9737
= 78.2 g/mol