Question

The internal energy change in joule when 90g of water undergoes complete evaporation is 100 degree celsius is

(Given : ∆Hᵥₐₚ for water at 373k = 41kJ / mol, R = 8.314JK⁻¹ mol⁻¹)

Answer 1

To calculate the internal energy change when 90g of water evaporates at 100 degrees Celsius, we convert the mass to moles, then multiply by the heat of vaporization, resulting in an internal energy change of 204,754 joules.

Step-by-step explanation:

The question pertains to the heat of vaporization of water. To find the internal energy change in joules when 90g of water undergoes complete evaporation at 100 degrees Celsius, we can use the provided heat of vaporization, ΔHᵖᵗᵕ for water at 373K (100°C) which is 41kJ/mol. First, we need to convert the mass of water to moles by using the molar mass of water (18.015 g/mol):

m (water) = 90g / 18.015 g/mol = 4.994 mol of water

Then, to find the internal energy change, we multiply this by the molar heat of vaporization:

ΔU = 4.994 mol × 41 kJ/mol = 204.754 kJ

Since we want our answer in joules, we convert kJ to J by multiplying by 1000:

ΔU = 204.754 kJ × 1000 = 204,754 J

Therefore, the internal energy change when 90g of water undergoes complete evaporation at 100 degrees Celsius is 204,754 joules.