Question

b. Will the solubility of the Salt Increase of uelede wilt lempirutur 4. A 5.00 g sample of KBr at 25.0°C dissolves in 25.0 mL of water also at 25.0°C. The final equilibrium temperature of the resulting solution is 18.1°C. What is the enthalpy of solution, AH, of KBr expressed in kJ/mol?

Answer 1

Mass of KBr

= 5.00 g

Molar mass of KBr

= 119 g/mol

The number of moles of KBr

5.00 g = 0.042 mol 119 g/mol

Volume of water

= 25,0 mL

Density of water

Tw6 I =

Mass of water

= 25.0 mL x1 g/mL = 25.0 g

Mass of solution is the sum of masses of water and KBr

Mass of solution

W = 25.09 +5.00 g = 30.0 g

Specific heat of solution is assumed to be approximately equal to the specific heat of water.

It is

S = 4.184 mol.° c

The temperature change

AT = T: -T; = 18.1°C – 25.0°C = -6.9°C

Heat lost by solution

q=W x S x 47

9 = 30.0 9 x 4.184 mol. CX(-6.9°C)

q= -866 )

The enthalpy change for dissolution of KBr is

ΔΗ, =

ΔΗ, = 866 ) 0.042 mol

ΔΗ, = 20613 mol

Convert unit from J/mol to kJ/mol

1 kJ AH, = 20613 mol“ 1000 J

k] AH, = 20.6 mol