The calcium carbonate (CaCO3) in antacid tablets reacts with dilute hydrochloric acid (HCl) according to the following balanced equation: CaCO3(s) + 2HCl(aq) → CaCl2(aq) + CO2(g) + H2O(l) ΔH < 0 5.1 Is the above reaction EXOTHERMIC or ENDOTHERMIC? Give a reason for the answer. An antacid tablet of mass 2 g is placed in HCl(aq). After 30 s the mass of the tablet was found to be 0.25 g. 5.2 Calculate the average rate (in g s⁻¹) of the above reaction. The antacid tablet contains 40% calcium carbonate. Another antacid tablet of mass 2 g is allowed to react completely with HCl(aq). 5.3 Calculate the volume of carbon dioxide, CO2(g) that will be collected at STP. Assume that all the CO2(g) produced is from the calcium carbonate. The reaction rate of similar antacid tablets with excess HCl(aq) of concentration 0.1 mol·dm⁻³ at DIFFERENT TEMPERATURES is measured. The graph below has been obtained.

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The calcium carbonate (CaCO3) in antacid tablets reacts with dilute hydrochloric acid (HCl) according to the following balanced equation: CaCO3(s) + 2HCl(aq) → CaCl2(aq) + CO2(g) + H2O(l) ΔH < 0 5.1 Is the above reaction EXOTHERMIC or ENDOTHERMIC? Give a reason for the answer - English General - NSC Physical Sciences - Question 5 - 2019 - Paper 2

Question 5

The calcium carbonate (CaCO3) in antacid tablets reacts with dilute hydrochloric acid (HCl) according to the following balanced equation: CaCO3(s) + 2HCl(aq) → CaCl... show full transcript

Worked Solution & Example Answer:The calcium carbonate (CaCO3) in antacid tablets reacts with dilute hydrochloric acid (HCl) according to the following balanced equation: CaCO3(s) + 2HCl(aq) → CaCl2(aq) + CO2(g) + H2O(l) ΔH < 0 5.1 Is the above reaction EXOTHERMIC or ENDOTHERMIC? Give a reason for the answer - English General - NSC Physical Sciences - Question 5 - 2019 - Paper 2

Step 1

5.1 Is the above reaction EXOTHERMIC or ENDOTHERMIC? Give a reason for the answer.

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Answer

This reaction is ENDOTHERMIC because the change in enthalpy (ΔH) is less than zero (ΔH < 0). This indicates that heat is absorbed from the surroundings during the reaction.

Step 2

5.2 Calculate the average rate (in g s⁻¹) of the above reaction.

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Answer

The average rate can be calculated using the formula:

$\text{Rate} = \frac{\Delta m}{\Delta t}$

The mass lost is 2 g - 0.25 g = 1.75 g and the time taken is 30 s.

Thus,

$\text{Rate} = \frac{1.75 \text{ g}}{30 \text{ s}} = 0.0583 \text{ g s}^{-1}$ .

Step 3

5.3 Calculate the volume of carbon dioxide, CO2(g) that will be collected at STP. Assume that all the CO2(g) produced is from the calcium carbonate.

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Answer

First, calculate the mass of calcium carbonate present in the tablet:

Mass of antacid tablet = 2 g Percentage of CaCO3 = 40%

Mass of CaCO3 = 2 g × 0.4 = 0.8 g.

Now, convert grams of CaCO3 to moles:

Molar mass of CaCO3 = 100 g/mol,

Moles of CaCO3 = 0.8 g / 100 g/mol = 0.008 mol.

According to the balanced equation:

1 mol of CaCO3 produces 1 mol of CO2.

Thus, 0.008 mol of CaCO3 produces 0.008 mol of CO2.

At STP, 1 mole of gas occupies 22.4 dm³;

Volume of CO2 = 0.008 mol × 22.4 dm³/mol = 0.1792 dm³.

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Questions answered

5.1 Is the above reaction EXOTHERMIC or ENDOTHERMIC? Give a reason for the answer.

5.2 Calculate the average rate (in g s⁻¹) of the above reaction.

5.3 Calculate the volume of carbon dioxide, CO2(g) that will be collected at STP. Assume that all the CO2(g) produced is from the calcium carbonate.

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