Question

Polyethylene is a synthetic polymer or plastic with many uses. 1.36 g of a polyethylene sample was dissolved in enough benzene to make 100. mL of solution, and the osmotic pressure was found to be 1.86 torr at 25oC. What is the approximate molar mass of the polyethylene?

Answer 1

Answer:

Molar mass = 1.111 × 10⁻⁵ g/mol

Explanation:

Given data:

Mass of polyethylene = 1.36 g

Volume = 100 mL   (0.1 L )

Pressure = 1.86 torr (1.86/760 = 0.003 atm)

Temperature = 25 °C = 25 °C + 273.15 = 298.15 K

Molar mass of polyethylene = ?

Solution :

PV =nRT

n = PV/RT

n = 0.003 atm × 0.1 L / 0.0821 atm. L . mol⁻¹ .k⁻¹  × 298.15 k

n = 0.0003 atm. L / 24.5 atm. L . mol⁻¹

n = 1.2245 × 10⁻⁵ mol

Molar mass = mass / number of moles

Molar mass = 1.36g / 1.2245 × 10⁻⁵ mol

Molar mass = 1.111 × 10⁻⁵ g/mol