Question

0.50g of a volatile liquid was introduced
into a globe sf 1000ml capacity. The globe
was heated to 91°C, so that all the liquid
vapourised exerted
a pressure of 190 mmHg.
Calculate the molecular mass of the lliquid.

Answer 1

Answer:

59.52g/mol

Explanation:

This question can be answered using the formula;

PV = nRT

Where;

P = pressure (atm)

V = volume (L)

R = gas constant (0.0821 Latm/molK)

T = temperature (K)

From the information provided:

P = 190mmHg = 190/760 = 0.25atm

V = 1000ml = 1000/1000 = 1L

n = number of moles = ?

T = 91°C = 91 + 273.15 = 364.15K

PV = nRT

0.25 × 1 = n × 0.0821 × 364.15

0.25 = 29.8967n

n = 0.25/29.8967

n = 0.0084mol

Mole = mass/molar mass

Molar mass = mass/mole

Molar mass = 0.50/0.0084

Molar mass = 59.5238

Hence, the molecular mass of the liquid is 59.52g/mol