A student used the apparatus below to determine the molar heat of combustion of propanol - HSC - SSCE Chemistry - Question 13 - 2004 - Paper 1

First, we need to establish the relationship between the heat released by burning the propanol and the heat absorbed by the water.

Using the formula: $q = m imes c imes riangle T$ where:

• $q$ = heat absorbed by the water
• $m$ = mass of water (200 g)
• $c$ = specific heat capacity of water (4.18 J g⁻¹ °C⁻¹)
• $\triangle T$ = change in temperature (final temperature - initial temperature).

The heat released by burning 1-propanol is calculated using: $q_{released} = n imes \Delta H_{combustion}$ where:

• $n$ = number of moles of 1-propanol burnt
• $\Delta H_{combustion}$ = molar heat of combustion (2021 kJ mol⁻¹).

First, calculate the number of moles of 1-propanol burnt: $n = \frac{0.60 g}{60.1 g mol⁻¹} = 0.00995 mol$

Now calculate the heat released: $q_{released} = 0.00995 mol imes 2021 kJ mol^{-1} = 20.11 kJ = 20110 J$

This heat is absorbed by the water.