* The copper was a orange/red colour before being submerged.
* While the silver nitrate AgNO3 was a clear colourless liquid.
* Immediately after the copper was submerged it turned black.
* The copper wire was resting on the bottom of the beaker.
* After prolonged submersion the wire became thicker as more precipitate was formed on the wire.
* After prolonged submersion the solution became a clear light blue solution.
* After 24 hours a silver/grey crystalline structure formed around the wire and on the bottom of the beaker.
Processed data table:
What I measured
Value (unit) 3sf
Mass of reacted Cu
Number of reacted Cu
% uncertainty = ±0.605
Mass of reacted Ag
Number of reacted Ag
0. 0167 mol
% uncertainty = ±0.166
Balanced chemical equation between copper and silver:
Cu (s) + 2Ag+ (aq)
→ Cu2+ (aq) + 2Ag (s)
Mass of reacted Cu: Uncertainty:
m(Cu)= Original weight – final weight
m(Cu)= 2.020 – 1.688 = ±0.001 + 0.001
m(Cu)= 0.332 g = ±0.002
Number of reacted Cu: Uncertainty:
n(Cu)= 0.00522 mol (3sf) n(Cu) % uncertainty = ±0.605
Mass of reacted Ag: Uncertainty:
m(Ag)= Original weight – final weight
m(Ag) = 105.139– 103.335 = 0.001 + 0.001
= 1.804 g = ±0.002
Number of reacted Ag: Uncertainty:
Mr(Ag) = 107.87 gmol-1
n(Ag) = 0.0167 mol (3sf) n(Ag) % uncertainty = ±0.111
Calculation of Ratio
n(Cu) : n(Ag)
0.00522 : 0.0167 total % uncertainty = ±0.111+0.605
1:3.20 % uncertainty = ±0.716
1:3 % uncertainty = ±0.7
This reaction is an example of a single replacement redox reaction, as the copper element replaces an element in a compound, silver nitrate producing silver and copper nitrate. During the reaction the silver is reduced as it gains electrons and the copper is oxidized as it loses electrons.
Cu (s) + 2AgNO3+ (aq)
→ Cu(NO3)2 (aq) + 2Ag (s)
The balanced equation shows that two moles of silver nitrate react with one mole of copper to produce one mole of copper nitrate and two moles of silver.
The molar ratio between Copper and Silver should be 1:2, which you can see by the coefficients in the balanced equation.
Therefore my hypothesis is wrong as I have 1 more mole of silver than I should have, therefore my mass of silver was larger than expected or the moles of copper was lower than expected and my mass of copper was lower than expected.
Yet our small precision error, or random error attributed to the precision of instruments is ±0.716%, which indicates that our range excludes the accepted value of 2. Therefore our must have some experimental error.
This experimental error can be determined as a percentage through the following formula:
This experimental error is incredibly large. As my systematic error is small, I can determine that experimental error is the cause of the deviation from the accepted value.
The random error in this experiment was due to the number of operations needed to determine the ratio therefore an increased level of accuracy in the equipment would have increased our ability to determine a more accurate result. Increasing accuracy in equipment would have aided the experiment although the accepted value was still outside the range of random error.
There are several possible factors for the large experimental error. The first and most prominent of these reasons is the likelihood of the silver crystals still being saturated with water. Due to the time constraints on the experiment there was limited time to leave the crystals drying in the oven, indicating the possibility of there being water contamination with the silver. This would have increased the measured mass of the silver and therefore increased the value of n(Ag) increasing our ratio. This experiment could be improved if the crystals were left to dry in the oven for a longer time period, which would enable all of the water molecules to evaporate and not contaminate our sample.
Another possibility as that during the decanting some crystals were removed from the beaker. This would have decreased the mass of silver, thus decreased the n(Ag) decreasing our ratio. As our ratio was larger than accepted value it is unlikely that this played a significant part in the experimental error of my experiment. To ensure that this would not effect a future experiment I would use a filtration system using filter paper instead of using a decanting method.
Experimental error could also have been generated through having an incorrect copper measurement. An incorrect copper measurement could have been caused by copper flecks flaking off the wire into the solution and then being decanted out, though our method did try to remove this possibility by adding more silver nitrate it is still a possibility. This would have meant that we calculated less moles of copper than actually reacted. To ensure that this would not effect our results we should have left the extra silver nitrate for longer to allow it too react with any left over copper flecks.