1.) A solution of NaOH was standardized. An average of 32.12mL of the base was r

Question

1.) A solution of NaOH was standardized. An average of 32.12mL of the base was required to titrate 10.00mL of .3501M HCl standard to a phenolphthalein end point. Calculate the concentration of an unknown H2SO4 solution if 10.00mL of the unknown H2SO4 solution required an average of 39.87mL of the standardized NaOH solution.

2.) A solution of NaOH was standardized. An average of 42.12mL of the base was required to titrate 15.00mL of .2878M HCl standard to its end point. The base was then used to determine the concentration of an unknown citric acid solution. Citric acid has three acidic protons and can be abbreviated H3Cit. Calculate the concentration of the unknown H3Cit solution if 10.00mL of the solution required an average of 46.87mL of the standardized base. (Assume that all three protons in H3Cit are titrated in the experiment.)

Explanation / Answer

1) from first data we can calculate the NaOH concentration :

      HCl + NaOH ------------------------> NaCl + H2O

C1V1 (for HCl) = C2 V2 (for NaOH)

0.3501 x 10 = C2 x 32.12

C2 = 0.1090 M

concentration of NaOH = 0.1090 M

now by using this NaOH concentration we can calculate the concentration of H2SO4

H2SO4 + 2 NaOH -------------------------> Na2SO4 + 2H2O

C1 V1 / n1 = C2 V2 / n2

C1 x 10 / 1 = 0.1090 x 39.87 / 2

C1 = 0.2173 M

concentration of H2SO4 = 0.2173 M

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