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How can a metal reactivity series be constructed and justified with…
How can a metal reactivity series be constructed and justified with evidence?
Equipment
Electrodes and electrolyte combination
Copper
copper sufate
Aluminium
aluminium oxide
Tin
Tin chloride
zinc
zinc oxide
Magnesium
Magnesium sulfate
lead
lead nitrate
Iron
Iron oxide
Salt Bridge
Chemical
Potassium Chloride solution
Is very safe to use
will be used for the salt bridge
Physical
Filter paper
is sturdy and strong enough to withdrew saturation
Therefore, Filter paper will be used for the material for the salt bridge
plain letter paper
Limited since when letter paper is soaked and becomes soggy. Leading to disintegrate and ceasing the electron flow in the circuit.
Will not be used as don't want to risk circuit breaking
Paper towel
it isn't very strong so when it is soaked in the salt, it is likely to tear and disintegrate which will break the circuit
Will not be used as don't want to risk circuit breaking
Wires
Round-ended wire
Limited as the electrodes do not have a cylindrical port for the end of the wire to be inserted into therefore it would have to be held there by hand.
Will not use this type of wire
Alligator-Jaw Clip
Limitation of this would be the difficulty of connecting the clip to the voltemeter
Despite the limitation, it is the best option to hold the electrodes in place
Beakers
Small beaker
will be used for the galvanic cells as only a small amount of electrolyte is needed
Large beaker
will not be used
Test tube
much too small to use for a galvanic cell but will be easier to see a metal displacement reaction and acid base reaction
Will be used for metal displacement and acid reactions
Acid for acid reaction
Hydrochloric acid
Is a weak acid so wont cause any damage to us or the equipment. Also doesn't react explosively with any of the metals
Will use HCl for experiment
Determining reactivity
Using galvanic cells
Would need to use voltmeter to determine direction of electron flow (to identify anode and cathode) and voltage as is the bigger difference in reactivity between the metals (to get rough idea how far apart they are on the reactivity table)
time is a major limitation, 21 tests would need to be completed with various trails for each in order to reduce the effect of random errors
Despite the amount of time it will take, we will use this method initially as it provides us with the most information about the reactivity of metals
Would need to test all possible combinations of metals in order to be confident in the series created
the anode (negative electrode) will disappear and the cathode (positive electrode) will become a metal and the mass will increase
to see it disappear would require lots of time and a large quantity of electrolyte to ensure that it doesn't reach its saturation point
this method will not be used as it will require too much time and can be determined quicker using a voltmeter
Using metal displacement reactions
Visual way to determine which metal is more reactive than the other. If displacement occurs, colour change may be seen and metal will be seen forming
limited as again it is more of a qualitative observation and some reactions are hard to tell if they have displaced or not
This will be the second port of call to help determine which metals are more reactive if the results from the galvanic cells are unclear
Acid reactions
Metals with higher reactivity will react more vigorously with the acid
Time reaction and observe it in order to determine reactivity
Limitation is that this type of observation is quite qualitative and is hard to get a definitive result from it
Going to use this method to double check and make s final decision about the reactivity of metals in the case that the other results aren't clear
Reduction of errors
Random
number of trials
The more times the experiment is repeated, the effect of random errors will be decreased. Where an average result can be calculated from the number of trials, allowing more reliable and accurate representation of results.
Therefore, at least two trials will be conducted to reduce random errors.
Additionally, the outliers in the results can be eliminated and the reliability can be increased.
Systematic
use calibrated equipment, voltmeters and scales, to eliminate zero errors.
Therefore, the equipment that will be used will be kept the same and consistent amongst the trials and will be ensured to be calibrated
and use the same equipment across the trials, to keep consistency if there is an error with the calibration of the device.
Variables
For galvanic cells
controlled variables
The duration of the reaction (s)
the amount of solution of electrolyte (mL) and the mass of electrodes (g)
the size of the beakers
the chemical and material used for the salt bridge
independent variable - the combination of the electrodes, along with its corresponding electrolyte, will be changed in each individual trial.
dependent variable - the voltage will be recorded fromt the voltemeter in volts (V)
For metal displacement
controlled variables
the mass of the metals (g) and amount of ionic solution (mL)
the beaker used
independent variable - different metals being used in the trials
dependent variable - mass of metal (g)
For acid reaction
controlled variables
the amount of the acid solution and metal in the beaker
the size of the beaker
the acid used and the pH of it
independent variable - the metals in the solution will be varied
dependent variable - the time taken for metals to fully react in seconds. to see which metal reacts the fastest.