Fig. 1 shows a student using a temperature probe and a balance to investigate the reaction of lithium with water. The lithium is kept under oil before use b...
Question 1 Report
Fig. 1 shows a student using a temperature probe and a balance to investigate the reaction of lithium with water. The lithium is kept under oil before use because it reacts with water vapour. The student adds a very small measured mass of lithium to 100 g of water. Bubbles of hydrogen gas form and the water becomes warmer.
(a) Give the gas formed in this reaction. [1]
(b) Describe one test for this gas. [1]
(c) Give the word equation for the reaction of lithium with water. [2]
(d) Describe the energy change shown by the temperature probe. [1]
(e) Give one safety precaution for this experiment. [1]
Answer Details
(a) The gas formed is hydrogen. [1]
(b) Test the gas with a lighted splint. Hydrogen gives a squeaky pop. [1]
(c) lithium + water → lithium hydroxide + hydrogen. [2]
(d) The temperature probe shows a temperature increase. Therefore the reaction is exothermic: it releases energy to the water and surroundings. [1]
(e) Wear eye protection. Other acceptable precautions include using a very small piece of lithium, handling lithium with forceps, or using a safety screen. [1]
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