Question

when 2.50g of ammonium chloride is dissolved in 100.0g of water the temperature falls by 1.70K. Calculate the enthalpy of solution of ammonium chloride, assuming a heat capacity of 4.2JK-1g-1 and a density of 1.00gmL-1 for all solutions

Answer 1

Weight of NH₄u = 2.5g.

Weight of water = 100g.

Total weight after mixing = 100 + 2.5 = 102.5g.

i.e weight of solution = 102.5g.

density of solution = 1g ml^-1

Heat capacity of solution = 4.2J/kg { K = kelvin, g gram }

Temperature change = 1.7Kelvin

Total heat change = m.c.T

For solution

m = mass os solution.

c = heat capacity of sol4.

T = temperature change.

As;

m = 102. g.

c = 4.2JK^-1g^-1

T = 1.7Kelvin

Therefore,

heat change = 102.5g x 4.2JK^-1g^-1 x 1.7K

For solution

Therefore, heat change = 731.85 Joules.

This heat change, in other words, is the Enthalapy for the solution.

Therefore, enthalapy of the solution = 731.85 Joules.