Question

It takes 330 j of energy to raise the temperature of 14.6 g of benzene from 21.0 °c to 28.7 °c at constant pressure. What is the constant-pressure molar heat capacity of benzene?

Answer 1

The mathematical expression for heat capacity at constant pressure is given as:

`Q=n* C_(p)* \Delta T` (1)

where, Q = heat capacity

`C_(p)` = molar heat capacity at constant pressure

`\Delta T` = change in temperature

n = number of moles

Therefore,
`\Delta T` =
`28.7^(o)C-21^(o)C`

=
`7.7 ^(o)C`

Number of moles =
`(given mass in g)/(molar mass)`

=
`(14.6 g )/(78.11 g/mol)`

= 0.186 mole

Put the values in formula (1)

`330 J=0.186 mole* C_(p)* (7.7 ^(o)C+ 273)` (conversion of degree Celsius into kelvin)

`C_(p) = (330 J)/(0.186 mole* 280.7 K)`

=
`(330 J)/(52.2102 mole K)`

= 6.32 J /mol K

Hence, molar heat capacity of benzene at constant pressure =
`6.32 Jmol^(-1) K^(-1)`