ENCE 433                                                                                          Dr. Alba Torrents

ENVIRONMENTAL ENGINEERING ANALYSIS                      Spring 2001

 

Homework Set # 1                             Out: February 1                     Due: February 8

 

SOLUTIONS

 

1.

Molality is grams of solute per kilogram of water.

 

 

2.

(a) The molecular weight of CO3-2 is 60.

 

(b) The molecular weight of Ca3(PO4)2 is 310. Because each Ca3(PO4)2  forms six positive and six negative charges,

 

 

3.

 

Mol. wt. CaSO4  = 136

      Mol. wt. Na2CO3  = 106

 

      This is really a titration problem.  We don't worry about normalities here because the stoichiometric coefficients of the reactants are equal.

 

      The number of moles of  CaSO4  to be softened is:

 

           

 

      About 10 tons.