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Discussion in 'DAT Discussions' started by andyjl, Apr 27, 2007.
What is the normality of a 1M solution of H3PO4 titrated with CaCl2?
Someone please explain
2PO43- + 3Ca2+ ----> Ca3(PO4)2
Calcium phosphate is insoluble by the way
1mol of phosphate reacts with 3/2 mol equiv. of Ca2+
N = 1(1.5) = 1.5
How do you know how to set up the equation that way and to ignore the other product HCl?
HCl will dissociate immediately...furthermore...chloride salts are soluble except for with Hg2 ++, Ag+, Pb++, Cu+...when you set up the equation you have to eliminate spectator ions. therefore...know the solubility rules...
However...the answer 1.5 assumes complete dissociation of H3PO4...don't really think of H3PO4 dissociating completely in Calcium Chloride
Here is another way to think of normailty
H3PO4 titrated with NaOH
1mol H3PO4 reacts with 3equiv NaOH/mol H3PO4
Does the problem mention anything about being titrated in basic solution?
No, that was it.
Could you write out the steps in finding the final equation
With normality questions....just make sure you know the definition of normality.
N = mol x equiv/mol
Most of our study guides use normality for acid base titrations only and a chemical equation is not needed...
But for redox titrations...the equation is needed...look in your chemistry textbook for redox titration problems