Page 390 - Chemistry eBook

Sample Regents Questions
Base your answers to questions 62 and 63 on the information below.
The diagram and balanced ionic equation below represent a voltaic cell with copper and silver electrodes and the reaction that occurs when the cell is operating.
Voltaic Cell
V
Wire Voltmeter Wire
Cu(s) electrode
Cu(s) + 2Ag+(aq)
Salt bridge
Ag(s) electrode
Cu2+(aq) + 2Ag(s)
Cu2+(aq)
Ag+(aq)
62 Describe the direction of electron flow in the external circuit in this operating cell. [1]
63 State the purpose of the salt bridge in this voltaic cell. [1]
Jan 2011 #62-63
Base your answers to questions 64 and 65 on the information below.
A 20.0-milliliter sample of HCl(aq) is completely neutralized by 32.0 milliliters of
0.50 M KOH(a
q).
64 Calculate the molarity of the HCl(aq). Your response must include both a numerical setup and the calculated result. [2]
65 According to the data, to what number of significant figures should the calculated molarity of the HCl(aq) be expressed? [1]
Answer
PS/Chem.–Jan. ’11 [11] [OVER]
62) Answer: Electrons flow from the copper electrode to the silver electrode.
-OR- The electron flow is from Cu to Ag in the external conductor. -OR- The electron flow is from the anode to the cathode.
Explanation: Electrons flow from the anode (Cu) to the cathode (Ag).
63) Answer: The salt bridge allows permits the migration of ions between the ions but prevents the solutions from mixing.
389 © UNIT 10: OXIDATION & REDUCTION