This data only shows up to the equivalence point, but had to kept going, it would (should)have been a mirror of what we got here.
We started with the NaOH in the buret at 10.2mL. We had a measurement at the end of the experiment of 20.2 mL NaOH, for a total of 10mL, or .01L of NaOH used. We had an initial measurement of 5.9mL HCl, and ended with 10.9mL HCl. we calculated 10.9mL- 5.9mL in order to find out that the total amount of HCl used was 5mL, or .005L. We knew that the molarity of the HCl was .2M, and we had to find the number of moels of HCl used. So, we multiplied .005 L by .2M in order to find that the number of moles of HCl that we used was .001 moles of HCl. We then had to find the number of moles of the NaOH, so we could then use that to find the concentration. In order to find the number of moles of NaOH, we multiplied the moles of our known substance, HCl, at .001 moles, by the molar ratio between HCl and NaOH in their balanced chemical equation. In the equation, they both have a coefficient of 1, so the molar ratio is one. This means that the number of moles of NaOH is equal to .001 moles * 1, for a grand total of .001 moles of NaOH. Now that we got that, we had to calculate the concentration of the NaOH, which we can now do, as we have both the volume of NaOH used, and the number of moles of NaOH used. In oreder to find the concentration, we filled in the formula for molarity with what we know. This came out to look like Molarity(concentration)= moles/L = .001 moles/ .01 L= 0.1M。 Thus, through the power of titration with a strong acid, we found the concentration of the strong base, NaOH, to be .1M.
Conclusion
In this lab, we used titration to explore the concepts of stoichiometry and equivalence points. We found the concentration of an unknown substance by mixing .2M HCl with the NaOH of unknown concentration in order to experimentally ascertain the concentration of the NaOH. We found the concentration of the NaOH to be .1M, half of the concentration of the HCl that we titrated it with. The accepted value for the concentration of the NaOH is .1M, so we had 0% error.
references
"Flinn SDS." MSDS Search. Web. 19 Sept. 2014. <http://www.flinnsci.com/msds-search.aspx>.