Question

A chemist who studies water samples did a demonstration of how to test for lead in water. She added a clear solution of potassium iodide to a clear solution of lead(II)iodide. Then a yellow swirling solid formed in the liquid.

What is most likely true about the yellow solid?

Answer 1

Ok, I can't give you the answer, but here are some things to think about:

Since she's testing for lead what do you think the yellow substance is? (Not pure lead so don't say that and it can't be lead potassium because that doesn't work. It's also not the water What else was used?)

Also, It was formed out of the two solutions: does the product have different properties than the first two? There is color change which is an indication of a certain type of reaction- (is it a physical reaction or a chemical reaction?).

Answer 2

The balanced equation for this reaction is;
\[Pb(NO _{3})_{2 }+ 2KI \rightarrow PbI _{2} + 2KNO _{3}\]
The change in colour is majorily due to the products formed during the reaction. So sticking up with that, u just have to see which one of the 2 , PbI2 and KNO3 gives u a yellow colour solid.
Solid KNO3 is a white powder and so when it is in the aqueous medium it dissolves and will give u a colour less solution.
PbI2 is a yellow colour solid. So I think the colour was mainly due to PbI2 ( lead iodide. )