Investigating the reactivity of Iron, Zinc, Magnesium and Copper while reacting 2g of each metal with 5cm3 of HCl of concentration 1mol/dm3 and measuring the volume of hydrogen formed in 60 seeconds.
Investigating the relative reactivity of metals using an acid
Research Question: Investigating the reactivity of Iron, Zinc, Magnesium and Copper while reacting 2g of each metal with 5cm3 of HCl of concentration 1mol/dm3 and measuring the volume of hydrogen formed in 60s.
Background information: Different metals show different levels of reactivity. Whether they are made to react with water, acids, oxygen or any other chemical, the order of reactivity is always similar. This means that the reactivity is a basic property of the metal rather than the other chemical. In this activity we use a set of controlled experiments with hydrochloric acid to place some common metals in a reactivity series. In these reactions, hydrogen and salt are the products. Reactivity of metals is a useful tool in predicting the products of simple displacement reactions involving two different metals, as well as providing an insight into why different metals are extracted from their ores in different manners.The reaction of metals with acids depends on the ability of the metal to release electrons. The more easily a metal releases electrons, the more rapidly it will react with acid, because the reaction also depends on the ability of H+ ions in the acid to gain electrons and form hydrogen gas, in the following process: 2H+ + 2e- → H2.The relative reactivity of metals can be used to organise them into an activity series. Once organised, an activity series helps us to predict if a reaction will occur when a piece of elemental metal is placed in water, an acid solution, or a solution containing the ion of another metal. 1
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Activity series are generally listed in order of decreasing reactivity. This means that in a metal activity series we would find the most reactive metals at the top. Only a few of the most reactive metals are able to displace hydrogen from water while a larger number will displace H+ from an acid. The least reactive metals are not able to displace hydrogen from either of these and are therefore found at the bottom of the series.
Organising the metals in this fashion also allows us to predict how the metals will react with each other. In a solution or compound, an elemental metal will displace any metal lower than it on the activity series.2
The overall pattern of reactivity:Metals above hydrogen in the reactivity series react with acids; those below hydrogen in the reactivity series don't ; Of the metals above hydrogen, reactivity increases the further up the reactivity series you go.3
Magnesium is very reactive, and the tube will get quite hot as It is an exothermic reaction - one in which heat is given off. The extra heat also increases the speed of reaction by increasing the number of collisions between particles, and so the reaction accelerates.
Hydrogen and a colourless solution of magnesium chloride are produced.
Mg(s) + 2HCl(aq) MgCl2(aq) + H2(g)
Zinc reacts steadily with Hydrochloric acid to give colourless solutions of zinc chloride .
Iron has a slower reaction with Hydrochloric acids to give iron(II) chloride. If the reaction were performed to completion, a very pale green solution would form.
Copper would react slowly as it is not a very reactive metal.
Formula used: Rate of reaction= volume of gas collected in 60s/60
Independent variable: The independent variable is the factor that you purposely change or control in order to see what effect it has. In this investigation it is the type of metal used with are : Iron, Zinc, Magnesium and Copper.
Dependent variable: A dependent variable is the variable that is tested and measured in a scientific experiment. When the independent variable is manipulated, a change in the dependent variable is observed and recorded. In this investigation the dependent variable is the volume of gas collected in 60 seconds and hence it is the rate of reaction.
Controlled variable: Controlled variables are factors that are kept constant throughout the investigation. They are kept unchanging so that they won't influence the outcome of the experiment. The table below demonstrates the different controlled variables for this investigation.
Chemicals and apparatus:
- Powdered Zinc
- Powdered Magnesium
- Powdered Iron
- Powdered Copper
- Electronic scale
- Test tube
- Measuring Cylinder
- Gas syringe
- 1 mol/dm3 HCl
- Take one test tube, make sure it is clean and has no residue from an earlier experiment.
- Take an electronic scale and weigh 2 grams of powdered zinc and then add the powdered zinc to a test tube using a spatula.
- Measure 5 cm3 of 1 mol/dm3 HCl using a measuring cylinder.
- Add the acid to the test tube with the zinc and quickly attach the gas syringe.
- Once the gas syringe is attached start the stopwatch for 60 seconds .
- after 60s are over record the volume of gas collected in the gas syringe.
- Take out the gas syringe and and all the contents of the test tube . Dispose all of the contents that were in the test tube safely.
- Wash and dry the test tube carefully making sure no residue is left .
- Repeat steps 2 to step 8 , using powdered Iron , powdered magnesium and powdered copper. Not down the volume of gas collected in 60 seconds each time.
- Record all values in a data table .
- Calculate the rate of reaction with the formula given above. Record these values in the data table.
- Repeat the entire experiment 3 times to find an average of all values.
Safety, Ethical and Environmental issues:
- Wear a lab coat
- Wear gloves, this is important as HCl is being used which is a low pH acid that can cause burns and severe skin damage.
- Wear safety goggles in case a reaction becomes to vigorous.
- Be careful while using glass apparatus as it could break if dropped and hurt others in the laboratory.
- Carefully transport and use the acid as if it is dropped others could slip and fall and it it is spilled on a platform someone might touch it and be injured.
- Carefully dispose the contents of the test-tube as they contain acid that can cause damage plants or animals.