NY Regents Chemistry Exam June 2022
During a laboratory activity, appropriate safety equipment is used and safety procedures are followed. A student constructs a voltaic cell with magnesium and copper electrodes. The diagram and net ionic equation below represent this cell and the reaction that occurs.
78 Identify the subatomic particles that flow through the wire as the cell operates. [1]
Explanation: In a voltaic cell, electrons flow through the wire, generating energy and allowing the cell to operate.
Answer: electrons
79 Compare the number of electrons lost to the number of electrons gained during the reaction in the operating cell. [1]
Explanation: The number of electrons lost should be equal to the number of electrons gained
Answer: equal
80 State the form of energy that is converted to electrical energy in the operating cell. [1]
Explanation: In a voltaic cell potential energy (chemical energy) is converted to electrical energy
Answer: potential energy
81 Write a balanced equation for the half-reaction that occurs in the copper half-cell when the cell operates. [1]
Explanation: From the overall equation, we can see Cu^2+ on the left and Cu(s) on the right. Now lets make an equation and add electrons.
Cu^2+(aq) --> Cu(s)
The charge on the left side is 2+ and on the right side is 0.
We need to add electrons so that the charge on both sides is the same.
Remember electrons are negative. If we add two electrons to the left side, the charge on the left side becomes 0 which is equal to the right side. Don't forget to put minus next to the e symbol! (e-)
Answer:Cu^2+(aq) + 2e- --> Cu(s)
82 Identify one metal from Table J that is more easily oxidized than Mg. [1]
Explanation: Table J lists metals from most active to least active. Most active metals are on the top. A metal that is more easily oxidized than Mg should be higher than Mg on Table J.
Answer: It cold be any of the following: Li Rb K Cs Ba Sr Ca Na