I have spent all afternoon (on Thanksgiving, no less) trying to figure out these post-lab questions. We had to produce a precipitate of a reaction of:

Question

1) 1 ml 1M Na2SO4 + 9mL 1M CaCl2
Our result was .569g
2) 5 ml 1M Na2SO4 + 5 ml 1M CaCl2
Our result was .01g
3) 9 ml 1M Na2SO4 + 1mL 1M CaCl2
Our result was .002g
The first question wanted to know "the number of moles of reactants used." I converted the mL to L and multipled by the 1M. So I got .001, .009, .005, etc. Am I missing something?
The second question asked for "the ratio of mole of reactants" of each.
Is it as easy as .001/.009, etc...?
The last question asked which ratio produced the most precipitate (the first one according to my lab results) and whether that data is consistent with the balanced equation. I am lost.

Answer 1

I think you have answered the first question and second question correctly. For the third question, here is what should have happened
Notice the equation is
Na2SO4(aq) + CaCl2(aq) == CaSO4(s) + 2NaCl(aq)

So 1 mole Na2SO4 reacts with 1 mole CaCl2 to produce 1 mole of the solid, CaSO4.
Thus 0.001 mole Na2SO4 + 0.009 CaCl2 should have produced 0.001 mole CaSO4.(ratio of 0.1)
0.005 mole Na2SO4 + 0.005 CaCl2 should have produced 0.005 mole CaSO4. (ratio 1)
0.009 moles Na2SO4 + 0.001 mole CaCl2 should ahve produced 0.001 mole CaSO4 (ratio of 9).
Your results are not consistent with the equation. The ratio of 1:1 should have produced the largest amount of CaSO4 since the equation is a ratio of 1:1.

Answer 2

I really appreciate your help.