Skip to content
MathsGenie logo
Quick links
Open app

Course home

  1. IGCSE
  3. Chemistry Edexcel
  5. Question bank

Energetics

MediumHard
12345678910111213141516171819202122232425262728293031323334353637383940
Question 11

A student investigated the temperature change when sodium hydrogencarbonate is added to a solution of citric acid. Their experimental plan was:

  • Pour 150 cm3 of citric acid solution into a polystyrene cup.
  • Measure the starting temperature of the solution.
  • Add 6.0 g of sodium hydrogencarbonate, stir, and record the minimum temperature reached.

Here are the student's results:

  • Volume of citric acid solution = 150 cm3
  • Mass of sodium hydrogencarbonate = 6.0 g
  • Starting temperature = 19.5∘C19.5^\circ\text{C}19.5∘C
  • Minimum temperature reached = 13.1∘C13.1^\circ\text{C}13.1∘C
a.

Why is it better to use a polystyrene cup rather than a glass beaker for this experiment?

[1]
b.

The equation for the reaction is:

3NaHCO3(aq)+H3C6H5O7(aq)→Na3C6H5O7(aq)+3H2O(l)+3CO2(g) 3\text{NaHCO}_3\text{(aq)} + \text{H}_3\text{C}_6\text{H}_5\text{O}_7\text{(aq)} \rightarrow \text{Na}_3\text{C}_6\text{H}_5\text{O}_7\text{(aq)} + 3\text{H}_2\text{O(l)} + 3\text{CO}_2\text{(g)} 3NaHCO3​(aq)+H3​C6​H5​O7​(aq)→Na3​C6​H5​O7​(aq)+3H2​O(l)+3CO2​(g)

Suggest one observation, other than the change in temperature, that could be made during this reaction.

[1]
c.

State whether this reaction is exothermic or endothermic, and justify your response.

[2]
d.

Calculate the heat energy change (in Joules) in this experiment using the expression:

heat energy change=volume of solution×4.2×temperature change \text{heat energy change} = \text{volume of solution} \times 4.2 \times \text{temperature change} heat energy change=volume of solution×4.2×temperature change
[2]

Energetics Questions

  1. IGCSE
  2. /Chemistry
  3. /Energetics