Question

A substance has the following properties:

Heat capacities:

1.34 J/g ^oC (solid)
3.02 J/g ^oC (liquid)
2.55 J/g ^oC (gas)

Heat of Fusion = 4.23 kJ/mole
Heat of Vaporization = 23.5 kJ/mole
Melting Point = -30.0 ^oC
Boiling Point = 88.5 ^oC
Molar Mass = 69.3 g/mole

How much energy (in kJ) would be needed to heat 555 g of this substance from 1 to 201^oC?

Answer 1

mass of the substance = 555 g

melting point is -30 C

and we have to calculate it from 1 to 201 C so it is present in liquid state .

and its boiling temperature is 88.5 C

so heat absobed at 1 to 88.5 C

molar mass = 69.3

moles = mass/ molecular mass

= 555/69.3= 8.008 mole

now heat required = mass * heat capacity * temperature difference

555 * 3.02 * 77.5 =129897.75 j

now latent heat for converting 88.5 C liquid to 88.5 gas vapourisation energy

heat = 23.5 * 8.008 =188.188 j

now 88.5 to 201 C

temperature difference (201-88.5)=112.5

heat = heat capacity in gas phase * mass * temperature diff.

2.55 * 555 *112.5 =159215.625 j

now total = 159215.625 + 188.188 + 129897.75 =289301.563

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