In an electrolysis experiment, the ammeter records a steady current of 1 A. The mass of copper deposited in 30 minutes is 0.66 g. Calculate the error in the...
Question 1 Report
In an electrolysis experiment, the ammeter records a steady current of 1 A. The mass of copper deposited in 30 minutes is 0.66 g. Calculate the error in the ammeter reading. [ Electrochemical equivalent of copper = 0.00033 g C\(^{-1}\)]
Answer Details
Error in the ammeter reading (electrolysis of copper)
By Faraday's first law, the true charge that passed is found from the mass deposited and the electrochemical equivalent \(z\):
\[ m = zQ \;\Rightarrow\; Q = \frac{m}{z} = \frac{0.66}{0.00033} = 2000\,\text{C} \]The time of the experiment is \(t = 30\,\text{min} = 1800\,\text{s}\), so the true (actual) current is:
\[ I_{\text{true}} = \frac{Q}{t} = \frac{2000}{1800} = 1.11\,\text{A} \]The ammeter reads \(1.0\,\text{A}\), so the error is:
\[ \text{error} = I_{\text{true}} - I_{\text{read}} = 1.11 - 1.00 = 0.11\,\text{A} \]The ammeter reads about \(0.11\,\text{A}\) too low (a percentage error of roughly \(10\%\)).
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