Question

A chemist carefully measures the amount of heat needed to raise the temperature of a 460.0 mg sample of C,H,Cl, from 0.3 °C to 13.6 °C. The experiment shows that 7.19 J of heat are needed. What can the chemist report for the molar heat capacity of C,H,C1,7 Round your answer to 3 significant digits. I Jmol. X 5 ?

Answer 1

Given:

Q = 7.19 J

m = 0.46 g

Ti = 0.3 oC

Tf = 13.6 oC

use:

Q = m*C*(Tf-Ti)

7.19 = 0.46*C*(13.6-0.3)

C = 1.175 J/g.oC

This is specific heat capacity.

Molar mass of C2H2Cl2,

MM = 2*MM(C) + 2*MM(H) + 2*MM(Cl)

= 2*12.01 + 2*1.008 + 2*35.45

= 96.936 g/mol

use:

molar heat capacity = specific heat capacity * molar mass

molar heat capacity = 1.175 J/g.oC * 96.936 g/mol

molar heat capacity = 1.139*10^2 J/mol.oC

molar heat capacity = 1.139*10^2 J/mol.K

Answer: 114 J/mol.K