Question

750 mt 2. Calculate the molecular weight of Freon-12, if 122.70 liters of its vapor at 200.00 C and 790.00 mm Hg has a mass of 397.00 g. Show your work. 3. Suppose a student performs this experiment and obtains a molecular weight of 70 g/mol for isopropyl alcohol. Give valid sources of error for what could have caused the molecular weight to be higher than expected. 4. Suppose a student performs this experiment and obtains a molecular weight of 65 g/mol for t-butyl alcohol. Give valid sources of error for what could have caused the molecular weight to be lower than expected.

Answer 1

2. Ans :-

From Ideal gas equation :

PV = nRT

PV = wRT/M .........................(1)

Where,

P = Pressure of gas = 790.00 mmHg = 1.03947 atm

V = Volume = 122.70 L

n = Number of moles of Freon-12

w = Mass of Freon-12 = 397.00 g

R = Universal gas constant = 0.0821 L atm K^-1.mol^-1

T = Temperature = 200.00 ⁰C = 473 K and

M = Molecular weight of Freon-12 = ?

Put all these values in equation (1),

M = wRT/PV

M = (397.00 g).(0.0821 L atm K^-1mol^-1).(473 K) / (1.03947 atm).(122.70 L)

= 120.875 g/mol

Hence, Molecular weight of Freon-12 = 120.875 g/mol