Fig. 1 shows limestone chips being added to hydrochloric acid in a school investigation. Carbon dioxide passes through a delivery tube into a gas syringe. T...
Question 1 Report
Fig. 1 shows limestone chips being added to hydrochloric acid in a school investigation. Carbon dioxide passes through a delivery tube into a gas syringe. The student repeats the experiment using equal masses of calcium carbonate with different chip sizes. Table 1 shows the time needed to collect the same volume of gas. The acid is in excess, so all the calcium carbonate can react. The student should wear eye protection because hydrochloric acid is corrosive.
| calcium carbonate form | time to collect 30 cm3 carbon dioxide / s |
|---|---|
| large chips | 84 |
| small chips | 35 |
(a) Give the formula of carbon dioxide. [1]
(b) Use particle collision ideas to account for the result for small chips. [2]
The diagram shows a particle model for a reaction between aqueous sodium carbonate and hydrochloric acid. In beaker A the acid is more concentrated than in beaker B, but both have the same volume. Each small circle represents an acid particle. A student measures carbon dioxide produced in the first 30 s. Table 1 gives the results. Sodium carbonate is a compound that reacts with acid to make carbon dioxide, water and a salt.
| beaker | carbon dioxide in first 30 s / cm3 |
|---|---|
| A | 42 |
| B | 18 |
(a) Describe one difference between the particle models. [1]
(b) Use Table 1 to calculate the difference in gas volume. [1]
(c) How does a more concentrated acid change the number of collisions? [1]
(d) Give one observation that shows a reaction is taking place. [1]
(e) Draw a conclusion linking concentration and rate. [1]
Answer Details
Calcium carbonate chips
- (a) Carbon dioxide is \(\mathrm{CO_2}\). [1]
- (b) Small chips have a larger surface area than large chips of the same mass. More acid particles can collide with calcium carbonate each second, so there are more successful collisions and gas is collected faster. [2]
Acid concentration
- (a) Beaker A has more acid particles in the same volume than beaker B. [1]
- (b) \[42\ \mathrm{cm^3}-18\ \mathrm{cm^3}=24\ \mathrm{cm^3}\] [1]
- (c) A more concentrated acid has more particles in a given volume, so it increases the number of collisions per second. [1]
- (d) Bubbles or fizzing are observed, showing carbon dioxide is being produced. [1]
- (e) Higher acid concentration gives a faster reaction. The more concentrated acid produced more carbon dioxide in the same 30 seconds. [1]
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