Show Adding magnesium metal to hydrochloric acid produces hydrogen gas. The magnesium dissolves to form magnesium chloride, MgCl2. Let's write a balanced equation for this reaction. (c) Copyright 2000. All rights reserved. This is intended as a class practical. It is best if the students work in pairs because setting up and starting the experiment requires more than one pair of hands. One student can add the magnesium ribbon to the acid and stopper the flask, while the other starts the stopclock. During the experiment, one student can take the readings while the other records them. The experiment itself takes only a few minutes. But allow at least 30 minutes to give students time to set up, take readings and draw graph. Hydrogen gas (extremely flammable) is generated in the experiment. Students should not have access to any source of ignition. EquipmentApparatus
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Teaching notesThe equation for the reaction is: magnesium + hydrochloric acid → magnesium chloride + hydrogen Mg(s) + 2HCl(aq) → MgCl2(aq) + H2(g) Students follow the rate of reaction between magnesium and the acid, by measuring the amount of gas produced at 10 second intervals. 3 cm of magnesium ribbon typically has a mass of 0.04 g and yields 40 cm3 of hydrogen when reacted with excess acid. 50 cm3 of 1M hydrochloric acid is a six-fold excess of acid. In this reaction, the magnesium and acid are gradually used up. However the acid is in excess, so it is mainly the loss of magnesium (surface area becomes smaller) that causes the change in the rate. If a graph of volume (y-axis) against time (x-axis) is drawn, the slope of the graph is steepest at the beginning. This shows that the reaction is fastest at the start. As the magnesium is used up, the rate falls. This can be seen on the graph, as the slope becomes less steep and then levels out when the reaction has stopped (when no more gas is produced). The reaction is exothermic, but the dilute acid is in excess and the rise in temperature is only of the order of 3.5˚C. There is some acceleration of the reaction rate due to the rise in temperature. Some students might notice the flask becoming slightly warm and they could be asked how this would affect the rate of reaction, and how they might adapt the experiment to make it a ‘fair test’. What type of reaction is hydrochloric acid and magnesium hydroxide?a) The reaction between magnesium hydroxide and hydrochloric acid is an example of neutralisation reaction. The hydroxide and hydrogen ions will combine to form water. The remaining ions combine to produce the salt of neutralisation. The salt is magnesium chloride.
What type of reaction is Mg 2hcl → MgCl2 h2?The answer is a. single displacement reaction. Single displacement reactions are those that involve the replacement of an element in another compound. In the reaction given, magnesium metal reacts with hydrochloric acid resulting in the formation of magnesium chloride and hydrogen gas.
Is the reaction between magnesium and hydrochloric acid exothermic?Magnesium and hydrochloric acid is exothermic as the temperature increases.
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