Question

1)

The following information is given for tin at 1atm:

boiling point = 2270 °C	ΔHvap(2270 °C) = 230 kJ/mol
melting point = 232 °C	ΔHfus(232 °C) = 7.07 kJ/mol
specific heat solid= 0.226 J/g°C
specific heat liquid = 0.243 J/g°C

What is ΔH in kJ for the process of freezing a 35.6 g sample of liquidt in at its normal melting point of 232 °C.

2)

The following information is given for antimony at 1atm:

boiling point = 1440 °C	ΔHvap(1440°C) = 195 kJ/mol
melting point = 631 °C	ΔHfus(631°C) = 19.6 kJ/mol
specific heat solid= 0.209 J/g°C
specific heat liquid = 0.259 J/g°C

kJ are required to melt a 27.1 g sample of solid antimony, Sb, at its normal melting point.

Answer 1

1)

Hfus = 7.07 KJ/mol

Molar mass of Sn = 118.7 g/mol

mass(Sn)= 35.6 g

use:

number of mol of Sn,

n = mass of Sn/molar mass of Sn

=(35.6 g)/(1.187*10^2 g/mol)

= 0.300 mol

Use:

ΔH freezing = -number of mol * Hfus

= -0.300 mol * 7.07 KJ/mol

= -2.12 KJ

Answer: -2.12 KJ

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