Chemistry and ions?!?!?!?

Question

This is a question on a chemistry lab that I recently did and I don't understand it at all! Please give me some help!!!!

It is possible to get a false-positive or a false-negative result when testing for ion? Propose a situation that could lead to a false-positive for a particular ion. Choose a different ion and show how a false negative could result. Which do you think is more likely to happen, a false positive or a false neagative result? Explain your reasoning.

that first part of the question is a statement not a question sorry!

could someone at least help explain, i dont need the examples!

Answer 1

False-positive is easy to explain; you have something else which gives a similar response. For example, you might decide to use phosphate as a test for calcium ions, but it would not be a very good one because many other metals also give insoluble white phosphates.

False-negative; earlier I said that this was impossible. Now I see two possible ways. The ion could be complexed, preventing it from reacting as expected. For example, Mg2+ is normally very easily precipitated as Mg(OH)2, but this does not happen when it is complexed with EDTA. The other way would be if the test reagent was intercepted somehow. You might have a reagent which gives you a colour test for A, but when A and B are present reacts with B instead, and does not undergo a colour change. When you get a false negative, it is called "interference".

Finding examples: there might be some in your text or notes.

Thanks for putting me straight.