Precipitation Reaction

[lan418]

The experiment is a basic kind of precipitation reaction, you have 2 solutions in two bottles and you add to drops of each solution onto a sheet of transparency and see if precipitate forms. Well, one particular reaction that has me wondering was the .1M NaOH. First we mixed it with 2 strong acids and of course no reaction. 2 transition metals gave 2 precipitate. BUT, in group II the alkaline metals, we mixed .5 M Mg(NO3)2 with .1 M NaOH and no reaction occurred. However, when we mixed the same NaOH of same molarity with .1 M Ca(NO3)2 one guy in my group deciding that it was a precipitate present. Does Calcium Hydroxide produce a precipitate? Does Mg(NO3)2 form a precipitate? I found it funny how one element from Group II form a precipitate(the one with calcium) but the reaction with Mg didnt. Maybe we did something wrong because i thought the same elements from the same group exhibit the same manner. then my lab partner said that the reason was because Calcium was a heavier metal and for this reason there was a precipitate for the Calcuim reaction. Is that right?

[lan418]

You've got to be kidding me. Out of all the Chemistry experts on here, i havent gotten one single reply...

[H2SO4]

try making it more clear or so mething.

[insane_alien]

try writing down the reactions then go check on the web if any of the products is insoluble if one or more is then you will get a solid formed. your post is hell to understand by the way.

[brokenbin]

The definition of precipitate is a salt (or anything else) that cannot be dissolved in water. The solubility of a substance is not decided by what group of element it is from. Sodium chloride dissolves easily, right?, now go home and dissolve potassium chloride. It is possible, but it takes much more water to dissolve the same ammount. Now, when you mix NaOH with Mg(NO3)2, there is no precipitation because all of the salt produced dissolved into the 4 drops of water. But when you mix NaOH and Ca(NO3)2, things become a little bit different becaue the product does not dissolve in water as easily as the previous one. Therefore, you've got precipitation. But if you add some more water to the product, you will see it disapear. The merely 4 drops of water gets saturated with only a little bit of the second salt.

[lan418]

Reaction:

 

Mg2+ + OH- ----> Mg(OH)2

 

Ca2+ + OH - ----> Ca(OH)2

 

Molarity values can be found in my first post.

 

Brokenbin, is there a specific reason why Calcium doesnt dissolve as easily as Magnesium? (i.e. different atomic weights, conformation)

[lan418]

Shame on all of you...