A cement worker adds water to a powdered calcium compound before repairing a wall. Fig. 1 shows the mixture in a bucket. The reaction causes the bucket to b...
Question 1 Report
A cement worker adds water to a powdered calcium compound before repairing a wall. Fig. 1 shows the mixture in a bucket. The reaction causes the bucket to become warm.
| Mass of calcium oxide / g | Temperature rise / degrees C |
|---|---|
| 2.0 | 8 |
| 4.0 | 15 |
| 6.0 | 22 |
(a) Give the term used for a reaction that warms its surroundings. [1]
(b) Use Table 1 to describe the pattern between mass and temperature rise. [2]
(c) Give one safety precaution when adding water to calcium oxide. [1]
The diagram shows a chemistry teacher measuring the temperature change when dilute hydrochloric acid is neutralised by sodium hydroxide solution. The flask is supported in a beaker of insulating material.
| Volume of sodium hydroxide added / cm3 | Temperature / degrees C |
|---|---|
| 0 | 20.0 |
| 20 | 26.4 |
| 40 | 29.1 |
| 60 | 27.5 |
(a) Record the volume giving the highest temperature. [1]
(b) Give the word equation for hydrochloric acid reacting with sodium hydroxide. [2]
(c) Describe one improvement that would reduce energy transfer from the reaction mixture. [2]
Answer Details
Labelled answer diagram:
Calcium oxide and water
- (a) A reaction that warms its surroundings is exothermic [1].
- (b) As the mass of calcium oxide increases [1], the temperature rise increases [1]. For example, increasing the mass from 2.0 g to 6.0 g raises the temperature change from 8 °C to 22 °C.
- (c) Wear safety goggles when adding water to calcium oxide [1]. Gloves or adding the water carefully are also acceptable because the reaction releases heat and the mixture may splash.
Neutralisation investigation
- (a) The highest recorded temperature is 29.1 °C, produced by 40 cm3 of sodium hydroxide [1].
- (b) hydrochloric acid + sodium hydroxide → sodium chloride + water [2]. The reactants are named correctly [1] and the salt and water products are named correctly [1].
- (c) Use a lid or cover [1] and use a polystyrene cup or extra insulation [1]. Both reduce thermal energy transfer from the warm reaction mixture to the surroundings, making the measured temperature change more reliable.
Download The App On Google Playstore
Everything you need to excel in your exams
