Chemistry

I need help on these three questions. For all three of them you're supposed to write a balanced equation for each neutralization. Then, to find the concentrations of the unknown solutions if the following reactions are found to reach equivalence by titration.
The three questions are:
5) 21.7 mL of 0.0500 M Ba(OH)2 is added to 35.0 mL of HCl of unknown concentration.
6) 25.0 mL of 0.200 M lithium hydroxide is added to 20.0 mL of phosphoric acid of unknown concentration.
7) 30.0 mL of 0.500 M hydrobromic acid is added to 38.0 mL of strontium hydroxide of unknown concentration.

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asked by Molly
  1. First, there is no way for me to know if these titrations have reached the equivalence point since the concn is unknown; however, I suspect what you really want to know is the concn of the unknown material
    Ba(OH)2 + 2HCl ==> 2H2O + BaCl2
    mols Ba(OH)2 = M x L = 0.0217 x 0.05 = apprx 0.00108
    Using the coefficients in the balanced equation, convert mols Ba(OH)2 to mols HCl. That's 0.00108 mols Ba(OH)2 x (2 mols HCl/1 mol Ba(OH)2) = 0.00216
    Then M HCl = mols HCl/L HCl = 0.00216/0.035 = apprx 0.062 but you need to go through and get these numbers more accurately.
    6 and 7 are done the same way but I would point out on #6 that you don't indicate how many of the H ions in H3PO4 have been titrated.

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    posted by DrBob222

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