Question

When a 7.00 g7.00 g sample of KBrKBr is dissolved in water in a calorimeter that has a total heat capacity of 2.72 kJ⋅K−1,2.72 kJ⋅K−1, the temperature decreases by 0.430 K.0.430 K. Calculate the molar heat of solution of KBr.

Answer 1

Answer : The molar heat of solution of KBr is 19.9 kJ/mol

Explanation :

Mass of KBr = 7.00 g

Molar mass of KBr = 119 g/mole

Heat capacity = 2.72 kJ/K

Change in temperature = 0.430 K

First we have to calculate the moles of KBr.

`\text{ Moles of }KBr=\frac{\text{ Mass of }KBr}{\text{ Molar mass of }KBr}=(7.00g)/(119g/mole)=0.0588moles`

Now we have to calculate the heat of the reaction.

`q=c* \Delta T`

where,

q = amount of heat = ?

`c` = heat capacity =
`2.72kJ/K`

`\Delta T` = change in temperature = 0.430 K

Now put all the given values in the above formula, we get:

`q=2.72kJ/K* 0.430K`

`q=1.17kJ`

Now we have to calculate the molar heat of solution of KBr.

`\text{Molar heat of solution of }KBr=(q)/(n)`

where,

n = number of moles of KBr

`\text{Molar heat of solution of }KBr=(1.17kJ)/(0.0588moles)=19.9kJ/mol`

Therefore, the molar heat of solution of KBr is 19.9 kJ/mol