A student investigates the reaction MgO(s) + 2 HCl(aq) → MgCl₂(aq) + H₂O(l)
CHEMISTRY · Single correct · A Level · Chemistry · Energetics · Energetics
Problem
A student investigates the reaction
MgO(s) + 2 HCl(aq) → MgCl₂(aq) + H₂O(l).
Two calorimetry trials are performed at 25 °C.
• Experiment 1: 5.00 g of MgO is added to 200.0 g of 1.50 M HCl. The temperature of the solution (c = 4.18 J g⁻¹ °C⁻¹) rises by 7.50 °C.
• Experiment 2: 5.00 g of MgO is added to 200.0 g of distilled water under identical conditions. The temperature rises by 1.10 °C.
In each trial, the total mass of the mixture is 205 g. What is ΔH for the reaction above, expressed in kJ mol⁻¹ of MgO? (Molar mass MgO = 40.3 g mol⁻¹.)
(a) −6.4kJmol−1
(b) −53kJmol−1
(c) −44kJmol−1
(d) +44kJmol−1