Download Tutorial 4 File

CHM 406 Engineering Chemistry
Tutorial Problem Set 4
1.
Explain the meanings of the following terms.
(a) Sacrificial anode.
(c) Acid
(b) Passivation.
(d) Flocculation
2.
What is the pH of the following solutions?
(a) 0.25 mol L-1 HCl
(b) 0.050 mol L-1 KOH
(use Kw = 1.00 x 10-14 at 25oC)
3.
What value of [H+] do the following pH values correspond to?
(a) pH = 2.76
pH = 8.40
4.
Is electroplating Al with Cr a good way to protect Al from corrosion? Explain.
5.
A fuel cell is designed to use ethanol (C2H5OH) as the fuel.
(a) What is the overall cell reaction?
(b) Suggest a half reaction for the cathode (i.e., oxidation of the fuel). Water may be a reactant for
this purpose.
(c) Suggest three possible applications of such a fuel cell.
6.
MgCO3 is an insoluble salt that occurs as a mineral. In contact with water containing certain
dissolved substances, a chemical reaction may occur which causes Mg2+ cations to dissolve in the
water. Write down balanced chemical equations for the reaction of MgCO3 with the following:
(a) Water containing dissolved CO2.
(b) Dilute aqueous H2SO4.