A certain substance has a heat of vaporization of 70.83 kJ / mol. 70.83 kJ/mol. At what Kelvin temperature will the vapor pressure be 5.00 5.00 times higher than it was at 331 K?

The answer to the question is

The temperature at which the vapor pressure will be 5.00 times higher than it was at 331 K is 353.0797 K.

Explanation:

To solve the question, we make use of the Clausius-Clapeyron equation as follows

Where P₁ = Initial pressure

P₂ = Final pressure

T₁ = Initial temperature = 331 K

T₂ = Final temperature

dvapH = ΔvapH = Heat of vaporization = 70.83 kJ / mol.

R = Universal gas constant = 8.3145. J K⁻¹ mol⁻¹

We are required to find the temperature when P₂ = 5 × P₁

Therefore we have

= or T₂ = = 353.0797 K

The vapor pressure be 5.00 times higher than it was at 331 K when the temperature is raised to 353.0797 K.

1. for the first question, we must find the mass of the anhydrous salt, mgso₄. the molar mass for mgso₄·7h₂o is 246.47 g/mol, while that of mgso₄ is 120.37 g/mol.7.834 g mgso₄·7h₂o * 1 mol mgso₄·7h₂o/246.47 g * 1 mol mgso₄/1 mol mgso₄·7h₂o * 20.37 g mgso₄/mol = 0.647 g mgso₄

2. mass of water = mass of sample - mass of anhydrous salemass of water = 7.834 - 0.647 = 7.19 gpercent water in hydrate = 7.19/7.834 * 100 = 91.74%