Quick questions on Calorimetry and q = mcΔT: VCE Chemistry Unit 3

Solution calorimetry. A reaction (often combustion or neutralisation) takes place in or under a known mass of water. The heat released raises the water's temperature. The heat absorbed by the water is calculated with q = mcΔT.

A bomb calorimeter is calibrated electrically. A heater of known voltage V and current I runs for time t, supplying:

A reaction (often combustion or neutralisation) takes place in or under a known mass of water. The heat released raises the water's temperature. The heat absorbed by the water is calculated with q = mcΔT.

A sample is burned in pure oxygen inside a sealed steel "bomb" surrounded by water. Because heat goes into multiple components (the steel bomb, the water jacket, the stirrer, the thermometer), the whole apparatus is calibrated with a known electrical input first. The calibration factor (CF, in J °C^-1) converts the measured ΔT directly into energy released.

State two advantages of a bomb calorimeter over a simple solution calorimeter for measuring the enthalpy of combustion. [2 marks]

A $1.500 \, \text{g}$ sample of methanol is burned in a bomb calorimeter with $\text{CF} = 3.45 \, \text{kJ/}^{\circ}\text{C}$. The temperature rises by $9.92^{\circ}\text{C}$. (a) Calculate the heat released.

A student uses solution calorimetry to measure neutralisation enthalpy. They mix $50.0 \, \text{mL}$ of $1.00 \, \text{mol/L}$ HCl with $50.0 \, \text{mL}$ of $1.00 \, \text{mol/L}$ NaOH and observe a temperature rise from $20.0$ to $26.8^{\circ}\text{C}$. (a) Calculate $q$.