Solution Manual - General Chemistry 10th edition - Chapter 7 - Exercises - Heat Capacity (Specific Heat) - Number 1 page 283

QUESTION

Calculate the quantity of heat, in kilojoules, (a) required to raise the temperature of 9.25 L of water from 22.0 to 29.4 °C; (b) associated with a 33.5 °C decrease in temperature in a 5.85 kg aluminum bar (specific heat of aluminium = 0.903 J g^-1 °C^-1)




SOLUTION

(a)

V _water         =   9.25 L

                   =   9.25 L x (1000 cm³ L^-1)

                   =   9250 cm³

ρ _water          =   1 g cm^-3

m _water         =   V . ρ

                   =   9250 cm³ x 1 g cm^-3

                   =   9250 g

Cp _water       =   4.18 J g^-1 °C^-1

dT              =   29.4 °C – 22.0 °C

                   =   7.4 °C

Q                =   m Cp dT

                   =   9250 g     x     4.18 J g^-1 °C^-1     x     7.4 °C

                   =   286.121 KJ

(b)

m _aluminium   =   5.85 kg

                      =   5850 g

Cp _aluminium  =   0.903 J g^-1 °C^-1

Q                   =   5850 g     x     0.903 J g^-1 °C^-1     x     (-33.5 °C)
                      =   -176965.425 J
                      =   -176.965425 KJ