ACT / science / current ACT
Chemistry
10 original practice questions. Open them in any order.
Independent preparation material, not an official test or score prediction.
How fast do marble chips react with hydrochloric acid?
Passage type: Research Summary
Calcium carbonate (CaCO3), the main compound in marble, reacts with hydrochloric acid (HCl) to produce calcium chloride (CaCl2), water, and carbon dioxide (CO2) gas:
CaCO3(s) + 2 HCl(aq) → CaCl2(aq) + H2O(l) + CO2(g)
A group of students studied factors that affect how quickly CO2 is produced. In each trial, they placed 2.0 g of CaCO3 in a flask, added 50.0 mL of HCl solution, and immediately closed the flask with a stopper. A tube led from the stopper to an upside-down graduated cylinder filled with water, so that the CO2 produced pushed water out of the cylinder. The students recorded the time needed to collect 40 mL of CO2. A shorter time indicates a faster reaction. In every trial, both CaCO3 and HCl were present in amounts greater than needed to produce 40 mL of CO2.
Experiment 1 The students used medium CaCO3 chips (each about 4 mm across) and HCl at 25°C. They varied the concentration of the HCl, measured in moles per liter (M).
Table 1
| HCl concentration (M) | Time to collect 40 mL of CO2 (s) |
|---|---|
| 0.5 | 180 |
| 1.0 | 90 |
| 1.5 | 61 |
| 2.0 | 45 |
Experiment 2 The students used 1.0 M HCl at 25°C. In each trial, the 2.0 g of CaCO3 was in a different form.
Table 2
| Form of the 2.0 g of CaCO3 | Time to collect 40 mL of CO2 (s) |
|---|---|
| Large chips (about 8 mm across) | 150 |
| Medium chips (about 4 mm across) | 90 |
| Small chips (about 2 mm across) | 48 |
| Powder | 12 |
Experiment 3 The students used medium CaCO3 chips and 1.0 M HCl. The flask was kept in a water bath so that the HCl and the flask stayed at a chosen temperature during each trial.
Table 3
| Temperature (°C) | Time to collect 40 mL of CO2 (s) |
|---|---|
| 15 | 150 |
| 25 | 90 |
| 35 | 52 |
| 45 | 30 |
Question 1 of 10 · easier
Science passage set — Research Summary (multiple choice, 4 options)
Read the science passage and answer the question. Choose the ONE best answer from the four choices. Calculators are not permitted.
According to Table 1, as the HCl concentration increased from 0.5 M to 2.0 M, the time needed to collect 40 mL of CO2:
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