Sunday, 26 April 2015

Metal Reactivity with Acid

The purpose of this experiment is to investigate the relative reactivity of a variety of metals. Extension ideas are provided to allow generalisation across acids and to also investigate the effect of acid concentration.

The more reactive a metal is, the faster it should react and thus the quicker it should evolve a set volume of Hydrogen.

Equipment

50ml measuring cylinders
Top pan balance with 0.01g resolution
Stop clock
Powdered samples of 4 different metals (e.g. Magnesium, Zinc, Copper, Iron)
Hydrochloric Acid
Conical flask
Bung with delivery tube
Water trough
Goggles

Method

Note - you will need to perform a preliminary test to find a suitable volume and concentration of acid and mass of metal to use to ensure a sufficient volume of gas is produced.

Set up the water trough with the 50ml measuring cylinder upturned to collect the gas produced over water.
Measure out your acid and place in the conical flask. Weigh out your metal powder and set to one side.
When you are ready tip the metal powder into the acid and place the bung with delivery tube into the conical flask, then start the stopclock.
Time how long it takes the metal to produce 25ml gas.
Repeat the test twice more, then repeat using a different metal.

To ensure that the effect you are seeing is just down to the metal you will need to ensure that some control variables are maintained. The mass of metal used, volume of acid used and concentration of acid used should all be the same. Additionally the metal powders should ideally have the same size of grain. Finally you should also try to control the temperature. There will be a heating effect due to the reaction and this in turn affects the rate at which the reaction occurs.

Safety

Do not use highly concentrated acid for this experiment as spills may cause damage to surfaces or burns to skin. Goggles should be worn at all times when working with liquid chemicals. The reaction produces Hydrogen gas which is explosive, so care should be taken that no naked flames are present during this experiment.