Question

Calculate the amount of heat needed to melt 91.5g of solid benzene ( C6H6 ) and bring it to a temperature of 60.6°C . Round your answer to 3 significant digits. Also, be sure your answer contains a unit symbol.

Answer 1

Answer: The amount of heat required for melting of benzene is 20.38 kJ

Explanation:

The processes involved in the given problem are:

$1.)C_6H_6(s)(5.5^oC)\rightleftharpoons C_6H_6(l)(5.5^oC)\\2.)C_6H_6(l)(5.5^oC)\rightleftharpoons C_6H_6(l)(60.6^oC)$

• For process 1:

To calculate the amount of heat required to melt the benzene at its melting point, we use the equation:

$q_1=m\times \Delta H_{fusion}$

where,

$q_1$ = amount of heat absorbed = ?

m = mass of benzene = 91.5 g

$\Delta H_{fusion}$ = enthalpy change for fusion = 127.40 J/g

Putting all the values in above equation, we get:

$q_1=91.5g\times 127.40J/g=11657.1J$

• For process 2:

To calculate the amount of heat absorbed at different temperature, we use the equation:

$q_2=m\times C_{p}\times (T_{2}-T_{1})$

where,

$C_{p}$ = specific heat capacity of benzene = 1.73 J/g°C

m = mass of benzene = 91.5 g

$T_2$ = final temperature  = 60.6°C

$T_1$ = initial temperature = 5.5°C

Putting values in above equation, we get:

$q_2=91.5\times 1.73J/g^oC\times (60.6-(5.5))^oC\\\\q_2=8722.05J$

Total heat absorbed = $q_1+q_2$

Total heat absorbed = $[11657.1+8722.05]J=20379.2=20.38kJ$

Hence, the amount of heat required for melting of benzene is 20.38 kJ