Question

The addition of 109 g potassium fluoride to 597 mL of water (d = 1.00 g/mL) causes the temperature to rise 3.10 °C. What is the ΔHsoln for KF?

Answer 1

Given that

Volume of water = 597 ml

Density of water = 1.00 g/ ml

Density = mass / volume

Therefore mass of water = mass/ density

= 597 ml/ 1.00 g/ ml

= 597 g

= 0.597kg

And energy q= dH

= - (specific heat of water * mass of water and temperature change)

= - 4.184 *0.597 kg *3.10

=- 7.74 kJ

Number of moles = amount in g / molar mass

=109 g/ 58.0967 g/ mole

= 1.88 mole

ΔHsoln for KF =total heat / number of moles

=- 7.74 kJ/ 1.88 mole

=- 4.12 KJ/ mole

Negative sign indicate released of heat