EK Chemistry Lecture 30 minute question for Lecture 4!

Hi all,
Number 79 page 145

After filtering out excess solid, a student adds HCL to Solution 1 in Table 1. He then adds a small amount of CaSO4, which dissolves completely. Which of the following also occurs in the new solution?

The answer is B) Undissociated HIO3 increases when the HCL is added.

Some additional info that you guys might want to know is that Solution 1 is saturated.

Why is it that when you add HCL (which dissociates to H+ and Cl-) it increases the amount of saturation possible? I thought Solution 1 was already saturated, so anything added to it would fall out of solution?

Hmmm, I think I may have just answered my own question.

Is it because 1) when you add more HCL you have to add it in liquid amounts (you can't just add HCl, you have to add it in a liquid form)

2) With the reaction H+ (+) IO3- -><- HIO3, you cannot achieve saturation. Is this because there is no way for solid to occur? Because you're always adding more liquid if you're adding more acid (or base).

 

But how would adding HCL increase the concentratino of solute, if the solution is already saturated?

If the solution is saturated with H+ then wouldn't it be impossible to add more H+? And this depends on if the solution is even saturated with H+ or not. Is it saturated with H+ or just Ca2+ and SO4 2-?

 

Obviously, if we added more Ca2+ or SO4 2- it would just precipitate out out of solution (since those two common ions are definitely saturated).

My confusion lies with whether or not the H+ + IO3- <---> HIO3 reaction is saturated too!

The only way I am interpreting this is that by adding more acid, we CANNOT add more acid merely by adding it as a powder. The only way I've heard of adding more acid is by adding it in a liquid form (meaning the HCl is dissolved in water). So if we're going to add more HCl to the solution, we're also increasing the volume of water and giving room for the H+ ions to "fit in."

Is my reasoning correct or flawed?