A recycling centre receives unlabelled strips of magnesium, iron, copper and zinc. A technician places a 0.50 g strip of each metal into 25 cm3 of the same ...
Question 1 Report
A recycling centre receives unlabelled strips of magnesium, iron, copper and zinc. A technician places a 0.50 g strip of each metal into 25 cm3 of the same dilute acid at room temperature. The gas is collected in the apparatus in Fig. 1. The number in Table 1 is the volume of gas collected after 100 s.
Fig. 1 Apparatus used to collect a gas
| metal | volume of gas after 100 s / cm3 |
|---|---|
| magnesium | 48 |
| iron | 16 |
| zinc | 31 |
| copper | 0 |
Table 1 Results from the recycling-centre test
(a) Use Table 1 to give the metal with the greatest reaction rate. [1]
(b) Describe one observation in the flask when magnesium reacts with the acid. [2]
(c) Complete the word equation for the reaction of iron with hydrochloric acid.
iron + hydrochloric acid → iron chloride + ............ [1]
(d) Use the results to put magnesium, zinc and iron in order of reactivity, starting with the most reactive. [2]
(e) Suggest why copper produced no hydrogen in this test. [2]
(f) Give one change that would make the volume of hydrogen collected from the iron strip in 100 s larger. [2]
Answer Details
The same mass of each metal was used and gas volume was measured after the same time, so a larger gas volume indicates a faster reaction.
- (a) Magnesium produced \(48\text{ cm}^3\), the largest volume, so it has the greatest reaction rate: magnesium. [1]
- (b) Magnesium shows bubbles or fizzing, and the strip gets smaller or dissolves. The flask may also become warmer. Any two. [2]
- (c) iron + hydrochloric acid → iron chloride + hydrogen. [1]
- (d) The order is magnesium, zinc, iron. Their volumes are \(48\), \(31\), and \(16\text{ cm}^3\), respectively. [2]
- (e) Copper is less reactive than hydrogen, so it cannot displace hydrogen from the acid. Therefore no hydrogen is produced. [2]
- (f) Use a higher acid concentration and a higher temperature. Smaller pieces or powdered iron increase surface area, and stirring is also valid. Any two changes. [2]
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