[santi69r]

Hi I would like some help with this question. i Have never done chemistry before and now am studying a small course in it. i was encounter with this question whih has me stumped and i cannot figure out how to wor it out. would be great if i could get some help thanks.

Name a salt solution that can be added to each of the following solutions that will cause only one precipitate to form. Write the equation of this precipitation including states?

a. sodium sulfide and sodium hydroxide.

b. Calcium Nitrate and Calcium Hydroxide.

I tried to figure out which salt solution could be used for the first question and got Na2CO3 which is sodium carbonate. I also had a go at putting it into a balanced equation but im pretty confident its not right.
Na2S +  + Na2CO3 = Na2CO3 + NaOH

[Arkcon]

You're going to have to review your text book for a table of general solubility rules.  Then you'll know what to exclude, from your very strangely worded question -- do they mean the two pairs are mixed together, or separately, or what? 

At any rate I'll give you one -- most common nitrates are soluble, so there is nothing you can add to precipitate that one.  So cross that one off the list.  That table in your textbook will give you other plans of attack for this problem.

[santi69r]

Name a salt solution that can be added to each of the following solutions that will cause only one precipitate to form. Write the equation of this precipitation, including states?
The question is asing to do each one separately.
a. sodium sulfide and sodium hydroxide do

b. calcium nitrate and calcium chloride

this is the exact question that was given to me in a practice test so theres not much i can do to change it.

[Arkcon]

Yeah, I can read it the first time ... so you can precip. either ion, of either salt, but not two at once to "win" this challenge.  Groovy.  So you have to be selective, right?

[macman104]

So santi69r, you're looking for something to add that will selectively precipitate, the Na⁺, the S^2- or the OH^-.  You need to look at your solubility table in your book for this problem.  Same thing for the second problem, something that will selectively precipitate Ca²⁺, NO₃^- or Cl^- but not all of them.

[santi69r]

thankyou