NSC Physical Sciences Rate and Extent of Reactions: For this investigation write dow

Question

For this investigation write down the:

5.1.1 Dependent variable:

The dependent variable is the rate of reaction, which is measured by the volume of carbon dioxide (CO₂) gas produced.

5.1.2 Independent variable:

The independent variable is the concentration of hydrochloric acid (HCl), which is kept constant in the experiments A, B, and C.

The carbon dioxide gas, CO₂(g), produced during EXPERIMENT A is collected in a gas syringe. The volume of gas collected is measured every 20 s and the results obtained are shown in the graph below.

What can be deduced from the graph regarding the RATE OF THE REACTION during the time interval:

5.2.1 20 s to 40 s:

The graph indicates that the rate of reaction is decreasing during this interval. The slope of the curve diminishes, suggesting that the production of CO₂ is slowing down.

5.2.2 60 s to 120 s:

In this interval, the volume of CO₂ reaches a plateau, indicating that the rate of reaction is zero. This shows that the reaction has essentially completed.

Calculate the average rate (in cm³·s⁻¹) at which CO₂(g) is produced in the experiment:

5.3 Average Rate:

The average rate of reaction can be calculated using the formula:

$$	ext{Average Rate} = rac{	ext{Volume of CO₂ produced}}{	ext{Time interval}}$$

The total volume of CO₂ collected from the graph is approximately 500 cm³ over a time span of 120 seconds. Thus,

$$	ext{Average Rate} = rac{500 	ext{ cm}^3 - 0 	ext{ cm}^3}{120 	ext{ s} - 0 	ext{ s}} = rac{500 	ext{ cm}^3}{120 	ext{ s}} = 4.17 	ext{ cm}^3	ext{s}^{-1}$$

How will the volume of CO₂(g) produced in experiment B compare to that produced in experiment A? Choose from GREATER THAN, SMALLER THAN OR EQUAL TO.

5.4 Experiment B:

The CO₂ volume produced in experiment B will be SMALLER THAN that produced in experiment A due to the lower concentration of HCl used in B, which leads to fewer effective collisions.

A graph is now drawn for experiment C on the same set of axes. How will the gradient of this graph compare to the gradient of graph for experiment A? Choose from GREATER THAN, SMALLER THAN OR EQUAL TO.

5.5 Experiment C:

The gradient of the graph for experiment C will be GREATER THAN that for experiment A because powdered CaCO₃ has a larger surface area compared to granules, resulting in more effective collisions per unit time.

Assume that the molar gas volume at 40 °C is 25.7 dm³·mol⁻¹. Calculate the mass of CaCO₃ used in experiment A.

5.6:

To calculate the mass of CaCO₃ used:

1. Find the number of moles of CO₂ produced:

$$n(	ext{CO}_2) = rac{V}{V_m} = rac{500 	ext{ cm}^3}{25700 	ext{ cm}^3/	ext{mol}} = 0.0195 	ext{ mol}$$

2. According to the reaction, 1 mol of CaCO₃ produces 1 mol of CO₂. Hence,

$$n(	ext{CaCO}_3) = n(	ext{CO}_2) = 0.0195 	ext{ mol}$$

3. Calculate mass:

$$	ext{mass} = n 	imes 	ext{molar mass of CaCO}_3 = 0.0195 	ext{ mol} 	imes 100 	ext{ g/mol} = 1.95 	ext{ g}$$

For this investigation write down the: 5.1.1 Dependent variable: The dependent variable is the rate of reaction, which is measured by the volume of carbon dioxide (CO₂) gas produced - NSC Physical Sciences - Question 5 - 2020 - Paper 2

Worked Solution & Example Answer:For this investigation write down the: 5.1.1 Dependent variable: The dependent variable is the rate of reaction, which is measured by the volume of carbon dioxide (CO₂) gas produced - NSC Physical Sciences - Question 5 - 2020 - Paper 2