In: Chemistry
The zinc content of a 1.03 g ore sample was determined by dissolving the ore in HCl, which reacts with the zinc. The excess HCl is then neutralized with with NaOH. The reaction of HCI with Zn is shown.
Zn(s)+2 HCl(aq) → ZnCl2 (aq) +H2 (g)
The ore was dissolved in 150 mL of 0.600 M HCI, and the resulting solution was diluted to a total volume of 300 mL. A 20.0 mL aliquot of the final solution required 8.22 mL of 0.539 M NaOH to neutralize the excess HCI. What is the mass percentage (%w/w) of Zn in the ore sample?
The amount of I (aq) in a solution can be determined by titration with a solution containing a known concentration of S2O32- (aq) (thiosulfate ion). The determination is based on the net ionic equation
2S2O32- (aq)+I3-(aq) -> S4O62-(aq) +3I- (aq)
Given that it requires 35.2 mL of 0.240 M Na2S2O3(aq) to titrate a 15.0 mL sample of I3- (aq), calculate the molarity of I3- (aq) in the solution.