Answer:
a) 15.2 kJ/g
b) 1367 kJ/mol
Explanation:
Given:
Mass of lactic acid = 0.5865 g
Heat capacity C of calorimeter = 4.812 kJ/C
Initial temperature, T1 = 23.10 C
Final temperature, T2 = 24.95 C
To determine:
Heat of combustion/gram and heat/mole lactic acid
Calculation:
Molar mass of lactic acid = 90.08 g/mol
[tex]moles\ lactic\ acid = \frac{0.5865g}{90.08g/mol} =0.00651\ moles[/tex]
The heat of combustion is given as:
[tex]H = C\Delta T= C(T2-T1)[/tex]
where C = heat capacity of calorimeter
T1 and T2 are the initial and final temperatures
[tex]H = C(T2-T1)=4.812kJ/C(24.95-23.10)C=8.90 kJ[/tex]
a) heat of combustion per gram
[tex]H = \frac{8.90kJ}{0.5865g} =15.2kJ/g[/tex]
b) heat of combustion per mole
[tex]H = \frac{8.90kJ}{0.00651moles} =1367kJ/mol[/tex]
