Okay so for chemistry class we were supposed to react sodium hydroxide (NaOH) with copper (II) sulfate pentahydrate(CuSO4*5H2O). It forms a precipitate copper (II) hydroxide (Cu(OH)2) and sodium sulfate (Na2SO4) which is dissolved in solution plus water (H2O).

Okay this is the equation we got. Is it right?
2NaOH+CuSO4*5H2O--> Cu(OH)2+Na2SO4 +5H2O

The teacher gave us .61g NaOH and we had to find out the amount of CuSO4*5H2O needed for the reaction. We got 1.9g. I think maybe this is the part we got wrong.

The products are filtered through a funnel. The filtrate turned pink when phenolphtalein was added. That means there was too much NaOH used.

Help! I can't figure out what we did wrong.

What molecular weights did you get?

Scratch that, I get 1.9g too.

Let's see.. NaOH is 39.9g/mol and CuSO4*5H20 is 249.41g/mol.

Maybe we did something wrong in the lab part of it. We added water to dissolve each reactant and then put them together and stirred them. After that we filtered it. Do you think maybe how much water we added would make a difference?

Not really, I'm not sure! It must have been something you've done but I don't know what :)

Oh I figured it out. Basically the lab was stupid and we just added a bunch more copper II sulfate pentahydrate so that it didn't turn pink. So if we had done the calculation wrong the first time it might have worked.

Thanks anyway.

Haha great! :D

Just for my own curiosity, what colour was the copper II sulfate pentahydrate that you added to the solution? Was it white, or blue?

If it was white, then it was just copper II sulfate (no pentahydrate). That would mess up your calculations. If it was blue, then it was the pentahydrate form, but there may have been too much H2O added (was it damp?). The extra H2O would mess up your measurements.

It was blue, so it was pentahydrate. But I don't know about it being damp. Maybe somehow there was condensation from people handling the beakers or something. I don't know.