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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 given off, a delivery tube should be connected to a conical flask sealed with a bung. The delivery tube should direct the gas into a measuring cylinder or an inverted graduated container filled with water, allowing for the collection and measurement of gas in cm³.
Step 2
Explain, in terms of bond breaking and bond making, why some reactions are exothermic.
Answer
Exothermic reactions involve the breaking of chemical bonds and the formation of new bonds. During the breaking of bonds, energy is absorbed, which is an endothermic process. However, when new bonds are formed, energy is released. If the energy released during bond making is greater than the energy absorbed during bond breaking, the overall reaction releases energy to the surroundings, resulting in a temperature increase. Hence, the reaction is 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 show that smaller lumps of calcium carbonate produce a higher volume of gas compared to larger lumps when reacting with the same concentration of hydrochloric acid. This is because smaller particles have a larger total surface area, which increases the frequency of collisions between the acid particles and the calcium carbonate. Similarly, increasing the concentration of hydrochloric acid results in more acid particles available to collide with the calcium carbonate, thus accelerating the reaction rate. Therefore, both the size of the lumps and the concentration directly influence the rate of reaction through the collision theory.