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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 + 2HCl → CaCl₂ + H₂O + CO₂ (a) A student wanted... 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 measure the volume of gas given off, a delivery tube should be used, connected to a flask sealed with a bung. The delivery tube should be directed to a gas jar filled with water or a measuring cylinder inverted over water to collect the gas. This setup ensures accurate measurement of the gas volume produced.
Step 2
Explain, in terms of bond breaking and bond making, why some reactions are exothermic.
Answer
In an exothermic reaction, the energy released during bond making is greater than the energy required to break the bonds of the reactants. Breaking bonds requires energy input, while forming new bonds releases energy. If the net energy change is negative, the reaction releases heat into the surroundings, making it 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 size of the lumps of calcium carbonate affects the reaction rate due to the surface area exposed for reaction. Smaller lumps have a larger surface area, allowing more frequent collisions with hydrochloric acid particles, leading to a faster reaction rate. As seen in the results, the small lumps at both concentrations produced significantly more gas than the large lumps. Moreover, increasing the concentration of hydrochloric acid increases the number of acid particles in a given volume, enhancing the likelihood of particle collisions. This is evident as the reaction with 1.00 mol dm⁻³ hydrochloric acid produced much more gas than at 0.50 mol dm⁻³ for both sizes.