ENCE 433 Dr. Alba Torrents

EXAMINATION I "SHOW ALL WORK" Fall 1996

Tuesday, October 8

1. Find the normality of the following solutions:

(a) 60 mg CO3-2/liter, given that carbonate participates in the precipitation reaction:

(b) 155 mg Ca3(PO4)2 /liter in the following dissolution reaction:

(c ) 60 mg CO₃^-2 /liter, given that carbonate participates in the following neutralization reaction:

(15 %)

2. The pH of 100,000 gal of sodium cyanide, NaCN, is to be reduced to pH 6.0 through the addition of HCl. If the analytical concentration of sodium cyanide is 10^-2M, calculate the initial pH and the weight of HCl which would be required to make the pH adjustment.

(15%)

3. Calculate the pH of the following sodium hydroxide, NaOH, solutions:

(A) 1.0x10-3 M

(B) 1.0x10-8 M

(20%)

4. Phenol is a weak acid that is used as a wood preservative

C₆H₅OH C₆H₅O^- + H⁺ K_a = 1.2x10^-10

1. Draw the log[C] vs pH diagram for a mM solution:

(15%)

b) What is the speciation at pH = 5 (estimate concentration of all the species)

(5%)

c) Use the graph to determine the pH of water solution after the addition of 10-3 M C₆H₅ONa

d) Set up the system of equations and solve it to numerically determine the pH of a 10^-3 M solution C₆H₅OH

(10%)

ADDITIONAL INFORMATION

Species	Gfo (Kcal/mole)	Hfo (Kcal/mole)
CO2 (gas)	-94.26	-94.05
CO2 (aq)	-92.31	-98.69
CaCO3 (s)	-269.78	-288.45
Ca+2 (aq)	-132.18	-129.77
HCO3-(aq)	-140.31	-165.15
H2O (gas) H2O (aq)	-54.63 -56.69	-57.80 -68.31

R = 1,987 cal /mole oK = 0.082 liter-atm deg-1 mole-1 = 8.31 joules deg-1 mole-1

PV = nRT

	O	S	N	Na	P	C	Ca	H	Cl
atom w.	16	32	14	23	31	12	40	1	35.5