CE 370 – Introduction to Environmental Engineering Homework 4 Page 1 of 1 CE 370 – Homework 4 Problem 1.
(2 points) Draw each of the following chemicals using the (1) structural approach, (2) linear approach, and (3) kinky approach. a.
2-Chloropropane b.
2-Chloropropene c.
Methanol Problem 2.
(3 points) Trinitrotoluene (TNT), C
7
H
5
N
3
O
6
, combines explosively with oxygen to produce CO
2
, water, and N
2
. Write a balanced chemical reaction and calculate the grams of oxygen required for each 100 g of TNT. Problem 3.
(3 points) Ethylene diamine tetra-acetic acid (EDTA, C
10
N
2
O
8
H
16
) is a water-soluble chemical that readily combines with metals, such as calcium, magnesium, and iron to prevent them from precipitating as solids. One EDTA molecule associates with one metal atom. A factory produces an aqueous wastewater that contains 20 mg/L calcium and collects the waste in 44-gallon drums. What mass of EDTA would need to be added to each drum to completely associate all of the calcium the barrel? Problem 4.
(4 points) Hydrochloric acid (HCl, pK
a
= -3) completely dissociates in water to H
+
and Cl
-
. Calculate the pH of water after 25 mg/L of HCl is added. Problem 5.
(4 points) The gas in a soda can is pure CO
2
with an approximate pressure of 3 atm. Calculate the concentration of dissolved CO
2
in the soda at 5°C in g/L. (K
H(CO2)
= 0.063532 mol/(L·atm) at 5°C). Problem 6.
(4 points) 0.5 grams of solid calcium sulfate, CaSO
4(s)
, is added to 1.0 L of pure water. Immediately, the solid begins to dissolve according to the following reaction: CaSO
4(s)
⇌
Ca
2+
+ SO
4
2-
. What is the concentration of dissolved sulfate in the water once equilibrium is reached? K
sp (CaSO4)
= 2·10
-5
. You should assume that 1 molecule of Ca
2+
and 1 molecule of SO
4
2-
is produced for each molecule of CaSO
4
dissolved.
