PRELIMINARY STAGE 2018
St. Francis Xavier: 47 points
Swedru SHS: 44 points
Pope John SHS: 39 points
ROUND 2 - SPEED RACE
QUESTION
In a typical voltaic cell in an electrical circuit, in which direction do the electrons flow in the external circuit (from one electrode to the other outside the cell)?
ANSWER: From the anode to the cathode
SOLUTION:
Oxidation at the anode releases electrons, which travel through the external wire (doing electrical work) to the cathode, where they are consumed in the reduction half-reaction.
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PRACTICE QUESTIONS
1. QUESTION: In a voltaic cell, in which direction does conventional current flow in the external circuit?
ANSWER: From the cathode to the anode
SOLUTION:
Conventional current flows opposite to the electrons, which move from the anode to the cathode.
2. QUESTION: In a voltaic cell, towards which electrode do the anions in the salt bridge move?
ANSWER: Towards the anode
SOLUTION:
Oxidation at the anode forms cations there, so anions move in to balance the charge.
3. QUESTION: In a voltaic cell with metal electrodes, at which electrode does the mass of the metal usually decrease?
ANSWER: At the anode
SOLUTION:
The anode metal is oxidised to ions that pass into the solution.
4. QUESTION: In a voltaic cell, towards which electrode do the cations in the salt bridge move?
ANSWER: Towards the cathode
SOLUTION:
Reduction at the cathode removes cations there, so cations move in to balance the charge.
5. QUESTION: Which electrode of a voltaic cell is its negative terminal?
ANSWER: The anode
SOLUTION:
Oxidation at the anode releases electrons into the external circuit.
6. QUESTION: In a Daniell cell, at which electrode is copper deposited?
ANSWER: At the cathode (the copper electrode)
SOLUTION:
$Cu^{2+}+2e^-\rightarrow Cu$