Page 397 - Chemistry eBook

Sample Regents Questions
Base your answers to questions 60 through 62 on the information below.
The diagram below represents an operating electrolytic cell used to plate silver onto a nickel key. As the cell operates, oxidation occurs at the silver electrode and the mass of the silver electrode decreases.
Power source
60 Identify the cathode in the cell. [1]
61 State the purpose of the power source in the cell. [1]
Ni(s)
AgNO (aq) 3
Ag(s) electrode
62 Explain, in terms of Ag atoms and Ag+(aq) ions, why the mass of the silver electrode decreases as the cell operates. [1]
Base your answers to questions 63 through 65 on the information below.
In a titration, a few drops of an indicator are added to a flask containing 35.0 milliliters
J
a
n
2
0
1
2
#
of HNO3(aq) of
solution is slowly added to the flask, the indicator changes color, showing the acid is neutralized.
unk
now
n con
cent
ratio
n.
After 3
0.0 mil
6
liliter
0
s of
0.1
-
6
5M
NaOH(aq)
2
63 64 65
P.S./Chem.–Jan. ’12
The volume of the NaOH(aq) solution is expressed to what number of significant figures? [1]
Complete the equation in your answer booklet for this neutralization reaction by writing the formula of each product. [1]
In the space in your answer booklet, show a numerical setup for calculating the concentration of the HNO3(aq) solution. [1]
Answer
[10]
60) Answer: The key
-OR- Ni
Explanation: The cathode is the object that is being plated. Also, in the picture, the key is attached to the negative part of the battery. In an electrolytic cell, the cathode is negative. Therefore, we know that the key is the cathode.
61) Answer: The cell needs electrical energy to start the reaction. Explanation: An electrolytic cell cannot start without an outside energy source.
62) Answer: Silver atoms lose electrons and become silver ions in the solution. -OR- Silver atoms are oxidized to silver ions.
UNIT 10: OXIDATION & REDUCTION © 396