Question

A 0.500-g sample of KCl is added to 50.0g of water in a calprimeter (Figure 5.12) If the temperature decreases by 1.05C. what is the approximate amount of heat involved in the dissolution of the KCl , assuming the heat capacity of the resulting solution is 4.18 J/gC? Is the reaction exothermic or endothermic?

Answer 1

Answer : The reaction is endothermic.

Explanation :

Formula used :

$Q=m\times c\times \Delta T$

where,

$\Delta T$ = change in temperature = $1.05^oC$

Q = heat involved in the dissolution of KCl = ?

m = mass = 0.500 + 50.0 = 50.5 g

c = specific heat of resulting solution = $4.18J/g^oC$

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

$Q=50.5g\times 4.18J/g^oC\times 1.05^oC$

$Q=+221.64J$

The heat involved in the dissolution of KCl is positive that means as the change in temperature decreases then the reaction is endothermic and as the change in temperature increases then the reaction is exothermic.

Hence, the reaction is endothermic.