Australia's Science Forum

Hello to all you knowledgeable people out there,

I've found some discrepancies between the The Laboratory's recipe and the old hand written/typed recipes for making up 2M copper sulfate. The 'bible' says to use dilute 0.1 sulfuric acid, and the typed noted use Conc. It seems to me that'll be quite a big difference!

What do you use?

I use dilute!

Sass

As I understand it, the acid is added to clear the solution so it is not murky. Therefore, I make up the solution with the copper sulfate first and then just add how ever much sulfuric acid is needed to clear the solution. I don't think the molarity is critical - just so it does the job!

Robbie

I use Conc.Sulfuric Acid,if cloudy.If not,I don't use anything
Cheers
Mother

I use Conc also.

Thanks everyone for your answers.

Why is it sometimes cloudy and not others?

It's the impurities in the Cu SO4 that make it cloudy
Now off the top of my head I think 1M is close to saturated will consult Book!

Ocker I think youre right. I did a quick look up and a saturated solution of CuSO4 is 22.3g/100ml.

The MW of CuSO4 is 249.7g therefore 1M is 249.7g/1L

Which works out at is 24.97g/100ml and 2M is nearly 50g /100ml. I would call that SUPER saturated.
Are my calculations and reasoning correct??


LizzieB
How did you make up the 2M solution?? I just checked "The Laboratory"are you sure you didn't mean a 0.2M solution??

I Concur but any extra will just form crystals in bottom of bottle!

2 M/L Cu SO4 .
When would a conc of 2M be required?

I, like Ocker am at saturation point at 1 M/L ish.

Anything else is just saturated.

Sorry everybody - am just catching up, and yes, there's a story to tell ....
Tuesday (when I posted this originally), I was getting organised for my final Cert lll prac. it's been quiet here, so I was looking through all my solutions for something that needed refilling. Found the 2M CuSO₄ bottle, and then checked The Laboratory - hence the query about the acid.
Now of course you've all figured out what happened next - it didn't dissolve! Actually it was a great demonstration - I went to my SI Data book, and found that a saturated solution is only 22g/100mL. Why do I have a 2M bottle - good question. There's been a succession of casual and untrained science assistants in this job, including me!
It was an interesting exercise, and good to realise that these days I know where to find the answers. That's mainly due to all of you, especially my local network and mentors, and what I've learnt here - so thank you all - though the more I learn, the more I realise how much there is yet to learn....
The best news is that I've now been signed off on all my Cert lll modules - Hooray!

Now if only the Uni course I started this year was that easy!

Hi All,

I came across this request last year for 2 M CuSO4 Solution.

If you look at solubility data on
http://encyclopedia.thefreedictionary.c ... lity+table
At 20 deg C it is 32 gms/100 ml and
at 30 deg C 37.8gms/100 ml.


Now looking at molecular weight and solubility data
I think it is possible to prepare solution with maximum concentration of
1.28 M at 20 deg C and
1.51 M at 30 deg C.
I think to be on safe side we can safely prepare 1.25 M solution
assuming minimum room temperature of around 20 deg C.

I hope it helps.

Cheers
NT

Ocker wrote:I Concur but any extra will just form crystals in bottom of bottle!

Speaking of crystals, Ive got a bunch of test tubes with CuSO4 crystals stuck fast at the bottom and no idea how to get them out. A few came loose with a vigorous shaking but most are stuck fast and resisting the test tube brush and and even a probe only gets a couple of bits out.
Any advice would be much appreciated.

Try Hot water!

Hot water is the go!

Sometimes may need to have a couple of goes at it, but hot water definitely does the trick.

Julie

put some hot water in the tubes and then sit the tubes in a beaker of water and then sit the beaker on your hotplate to create a hot water bath might help as well.