Question

22 Determine the molar mass of an unknown gas that has a volume of 72.5 mL at a temperature of 68C, and a pressure of 0.980 atm and a mass of 0.207 g.

Answer 1

81.5g/mol

Step-by-step explanation:

Molar mass is the ratio between mass of a substance (In this case, 0.207g) and moles presents in this mass.

To solve this question we must find the moles of the gas in order to obtain the molar mass using:

PV = nRT

PV / RT = n

Where P is pressure = 0.980atm

V is volume in Liters = 0.0725L

R is gas constant = 0.082atmL/molK

T is absolute temperature = 68°C + 273.15 = 341.15K

0.980atm*0.0725L / 0.082atmL/molK*341.15K = n

2.54x10⁻³ moles = n

Thus, the molar mass of the gas is:

0.207g / 2.54x10⁻³ moles

81.5g/mol