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:
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.
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.
I really appreciate your help.
It seems like you're having trouble with some post-lab questions related to a reaction where you produced a precipitate by mixing different solutions. Let's go through each question step by step to help you find the answers.
1) To find the number of moles of reactants used in the first reaction, you correctly converted the mL to L and multiplied by the concentration (1M). So for the first reaction, you would have:
- Na2SO4: (1 mL / 1000 mL) * 1 M = 0.001 moles
- CaCl2: (9 mL / 1000 mL) * 1 M = 0.009 moles
Your calculations seem to be correct here.
2) For the second question, which asks for the ratio of moles of reactants in each reaction, you can simply divide the number of moles you calculated for each reactant. For the second reaction:
- Ratio = (0.001 moles Na2SO4) / (0.001 moles CaCl2) = 1
So the ratio of moles of Na2SO4 to CaCl2 in the second reaction is 1:1.
You can apply the same approach to find the ratios for the other reactions.
3) The last question asks about the reaction that produced the most precipitate and whether the data is consistent with the balanced equation. From your lab results, it seems like the first reaction produced the most precipitate with a yield of 0.569g. To check if your data is consistent with the balanced equation, you need to compare the stoichiometry of the balanced equation with your experimental results.
Based on the information you provided, the balanced equation for the reaction could be:
Na2SO4 + CaCl2 -> 2NaCl + CaSO4
According to the balanced equation, for every mole of Na2SO4 and CaCl2, you should theoretically get 1 mole of CaSO4 precipitate. This means that the ratio of the moles of precipitate (CaSO4) to Na2SO4 or CaCl2 should be 1:1.
To check if your data is consistent, you can calculate the moles of precipitate produced in each reaction:
- 1st reaction: 0.569g CaSO4 / molar mass of CaSO4 = X moles
- 2nd reaction: 0.01g CaSO4 / molar mass of CaSO4 = Y moles
- 3rd reaction: 0.002g CaSO4 / molar mass of CaSO4 = Z moles
Compare the calculated mole ratios of the precipitate to the mole ratios of the reactants in each reaction. If the ratios are close to 1:1, then your data is consistent with the balanced equation.
I hope this explanation helps you understand how to approach these post-lab questions. If you have any further doubts or need additional assistance, feel free to ask!