Question

When a 6.00 g sample of KCl is dissolved in water in a calorimeter that has a total heat capacity of 6.92 kJ ⋅ K − 1 , the temperature decreases by 0.200 K . Calculate the molar heat of solution of KCl .

Answer 1

Answer:

Molar heat of solution of KCl = -17.1965kJ/mol

Explanation:

Given Values:

The temperature change = 0.200 K

Mass of KCl = 6.00 g.

Calorimeter heat capacity = 6.92 kJ/K

Heat absorbed by the calorimeter is calculated

Q=CΔT

Where,

Q = amount of heat.

C= the heat capacity.

ΔT = the change in temperature.

Substitution of the values in the equation above.

Q​=​6.92​k​J​/​K​×​0.200​K​=​1.384​k​J

Heat released by the solution = Heat absorbed by the calorimeter.

Heat evolved by s​o​l​u​t​i​o​n​=​−​Q​c​a​l​o​r​i​m​e​t​e​r (heat gained by calorimeter)​=​−​1.384​k​J

Now, number of moles of KCl is given by

n=W/M

Where,

n = number of moles.

W = mass of KCl .

M = molar mass of KCl = 74.5513g/mol

Substituting in the above equation above we have.

n​=​6.0​0g​/74.5513​g​/​m​o​l​=​0.08048 ​m​o​l

The enthalpy change of the reaction is given by

Δ​H​s​o​l​u​t​i​o​n per mole​=​−​1.384​k​J/ 0.08048​m​o​l

​Δ​H​s​o​l​u​t​i​o​n​=​−​17.1965kJ/mol

Therefore the enthalpy for the solution

-17.1965kJ/mol

molar heat of solution of KCl = -17.1965kJ/mol