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A student was asked to perform a first-hand investigation to measure the difference in potential of various combinations of metals in an electrolyte solution - HSC - SSCE Chemistry - Question 19 - 2006 - Paper 1
Question 19
A student was asked to perform a first-hand investigation to measure the difference in potential of various combinations of metals in an electrolyte solution. The st... show full transcript
Worked Solution & Example Answer:A student was asked to perform a first-hand investigation to measure the difference in potential of various combinations of metals in an electrolyte solution - HSC - SSCE Chemistry - Question 19 - 2006 - Paper 1
Step 1
Identify which combination of the metals supplied should give the highest potential difference.
Answer
The combination of silver and zinc should give the highest potential difference because silver has a higher standard electrode potential compared to the other metals provided (aluminium and zinc). This allows for a larger voltage to be generated when paired with zinc, which has a lower potential.
Step 2
Sketch and label a diagram of an experimental setup that the student could use with the combination of metals identified in part (a).
Answer
The diagram should include two electrodes (one made of silver and the other of zinc) immersed in an electrolyte solution containing zinc nitrate. Wires connecting the electrodes to a voltmeter to measure the potential difference should also be included. The setup should indicate the salt bridge connecting the two electrolytes.
Step 3
Write a balanced chemical equation for the overall reaction for the metals identified in part (a), and calculate the expected potential difference.
Answer
The balanced chemical reaction between silver ions and zinc is:
ightarrow ext{Zn}^{2+} (aq) + 2 ext{Ag (s)}$$ To calculate the expected potential difference, we use standard electrode potentials (E°): - E°(Ag+/Ag) = +0.80 V - E°(Zn²+/Zn) = -0.76 V The expected potential difference is: $$E°_{cell} = E°_{cathode} - E°_{anode} = E°(Ag) - E°(Zn) = 0.80 - (-0.76) = 1.56 ext{ V}$$Step 4
Outline steps the student could have taken to minimise this variation.
Answer
- Ensure that all connections and electrodes are clean to reduce resistance and improve conductivity.
- Use a standard concentration of electrolyte to avoid variability in ion availability.
- Conduct multiple trials and average the results to account for anomalies.
- Maintain a constant temperature during the experiment as temperature variations can impact potential difference.