Question

10. A calorimeter is constructed from copper and contains 550 mL of water initially at

21.3°C. If 5.00 g of propane are burned in the calorimeter raising the temperature to
31.0°C, what is the mass of the copper calorimeter? (The molar enthalpy change of
combustion of propane is -2043.9 kJ/mol).

Answer 1

To answer this, we need to use the heat capacity formula, q = mcΔT, and the molar enthalpy of combustion.

First, calculate the heat absorbed by the water:

q_water = mcΔT

= (550 g)(4.18 J/g°C)(31.0°C - 21.3°C)

= 22,300 J

Next, calculate the heat produced by the combustion of propane:

q_propane = -2043.9 kJ/mol * (5.00 g / 44.09 g/mol)

= -232,000 J

The heat absorbed by the water and the calorimeter is equal to the heat produced by the combustion of propane. Therefore, the heat absorbed by the calorimeter is:

q_calorimeter = q_propane - q_water

= -232,000 J - 22,300 J

= -209,700 J

Finally, calculate the mass of the copper calorimeter:

m_calorimeter = q_calorimeter / (c_copper * ΔT)

= -209,700 J / (0.385 J/g°C * (31.0°C - 21.3°C))

= 1500 g

So, the mass of the copper calorimeter is approximately 1500 g.