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P-4
ADVANCE STUDY ASSIGNMENT
1.
A current of 100 mA is used to electrolyze a dilute solution of sulfuric acid for 1 hour and 30 minutes.
How many coulombs of electricity were used? Note that one ampere equals 1000 milliampere (mA). Answer: 5
2.
What is the vapor pressure of water at 22.3 °C? Use linear interpolation to calculate the value.
Answer: 20.2 mm Hg
3.
In words, what is a Faraday (do not just give the value of the Faraday)?
Answer: charge on 1 mole of electrons.
4.
A student used a current of 140 mA for 30.0 minutes to electrolyze a dilute aqueous solution of sulfuric
acid. A volume of 35.00 mL of hydrogen was produced at 22.3 °C and 701 mm of Hg. The height of
the water column in the buret after electrolysis was 10.0 cm. What value should the student report for
the value of the Faraday?
Answer: 98,400 C
5.
The student in problem (4) found that the mass of the copper electrode had decreased by 0.090 g.
Combining this information with the amount of hydrogen produced (Problem 4), what answer should
be reported for the molar mass of copper?
Answer: 7.0 x 10¹ g/mol.
6.
A student noticed that the end of the copper wire in the H2SO
4
solution had become very thin, and that
simultaneously, the current had decreased. Explain why the current decreased.
7.
What would happen if copper ions were allowed to build up in the solution? Why?
