Why is it necessary to separate ions through precipitation and dissolution react

Question

Why is it necessary to separate ions through precipitation and dissolution reactions before identification of the ion can occur? If ions are not separated, horrible chemical reactions occur which produce foul smelling concoctions. This is to avoid the possible interference of one ion with another. If ions are not separated, the waste material is too difficult to dispose of. It is not needed, one ion can always be identified in the presence of other ions, the observation is made that ion B precipitates with HCI while ion A does not HCI is added to a solution possibly containing A and/or B. Precipitation occurs in the solution. Which one of the following is a true statement? A is present and B is not present. Both A and B are present. Neither A nor B are present. A is present, but don't know about B. B is present, but don't know about A. Using the titration curve at the end of this exam, what is the volume of sodium hydroxide required to titrate the unknown acid to the equivalence point? 15 mL 20. mL 30. mL 40. mL Using the same titration curve as in problem #26, determine the K_a of the unknown weak acid. 6 times 10^-3 6 times 10^-5 6 times 10^-7 6 times 10^-9 What is the Molarity of a 30.00 mL sample of a monoprotic weak add that required 35.25 mL of 0.0942 M NaOH to reach the equivalence point? 0.0825 M 0.111 M 0.249 M 0.300 M

Explanation / Answer

1) It is necessary to separate ions through precipitation and dissolution reaction before identification of ion is carried out because, presence of more than one ion in the mixture may interfere in one or another way in the identification process.

For example, the formation of a yellow precipitate upon addition of aqueous S2- confirms the presence of Cd2+ in a solution. But the test shows a negative report if present along with Pb2+ or Cu2+ since they will form a black precipitate with added S2-.

Ans- Option b

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