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Calcium carbonate reacts with dilute hydrochloric acid to produce calcium chloride, water and carbon dioxide - Edexcel - GCSE Chemistry Combined Science - Question 5 - 2019 - Paper 1
Question 5
Calcium carbonate reacts with dilute hydrochloric acid to produce calcium chloride, water and carbon dioxide. CaCO₃ + 2 HCl → CaCl₂ + H₂O + CO₂ (a) A student wante... show full transcript
Worked Solution & Example Answer:Calcium carbonate reacts with dilute hydrochloric acid to produce calcium chloride, water and carbon dioxide - Edexcel - GCSE Chemistry Combined Science - Question 5 - 2019 - Paper 1
Step 1
Complete Figure 3 to show the apparatus that could be used to measure accurately the volume of gas given off in two minutes.
Answer
To accurately measure the volume of gas produced in the reaction, a delivery tube should be connected to the conical flask containing the reactants. The delivery tube must lead into an inverted measuring cylinder or gas jar filled with water. This setup allows for the cumulative measurement of gas volume collected over the two-minute period.
Step 2
Explain, in terms of bond breaking and bond making, why some reactions are exothermic.
Answer
Reactions that are exothermic release energy due to the process of bond making exceeding the energy required for bond breaking. In bond breaking, energy is absorbed to break the bonds in the reactants, while in bond making, energy is released when new bonds form in the products. If the total energy released during the formation of product bonds is greater than the total energy needed to break the initial bonds, the excess energy is released as heat, marking the reaction as exothermic.
Step 3
Explain, in terms of collision of particles, how these results show the effect of the size of the lumps of calcium carbonate and the effect of the concentration of the acid on the rate of this reaction.
Answer
The results indicate that smaller lumps of calcium carbonate produce a greater volume of gas compared to larger lumps under the same conditions. This is because smaller particles have a larger surface area relative to their volume, leading to more collisions between the reactants. Additionally, higher concentrations of hydrochloric acid provide more acid particles per unit volume, increasing the likelihood of effective collisions. Consequently, the reaction rate is faster in the presence of smaller lumps and higher acid concentration, thereby generating more gas in a shorter time period.