Copper sulfate soultion

[Jazz]

this is first time i've heard about that. I add sulfuric acid to iron 11 sulfate only

[Labbie]

Sorry I put these two together because I felt it answered the Sulfuric acid with Copper sulfate, but it does not. So please do a search and when you find it let me know and I'll add it on.

[mikah]

Thank you for the reply. I think it was a printing error in the book and have crossed out that line for whoever inherits the book after me..

[Labbie]

I also do add sulfuric acid to my copper sulfate always have always will. Dr Robb If I remember correctly said it keeps better.

[AnnNos]

The addition of acid allows better separation of the iron ions and the sulfate ions in electrolytic experiments, especially in low molarity copper sulfate solutions.

[rae]

I always add 1ml of conc H2SO4 to my Copper sulfate when I make it up. It stops the yellow precipitate coming out and keeps it a nice blue colour. Not sure what the precipitate is but the acid helps.

[Jazz]

all you need is to filter through, it is blue again

[Labbie]

Hi All,

Just to make things a little easier, as acidifying solutions give the Metal Salts, (And, I don't know if you have noticed but it is metal salts only that you acidify), keeps the ionic separation rather than allowing the oxidation of these solutions of interest.

This also accounts for keeping a high pH within reactions which inturn will/can speed up typical reaction, the effect is like raising the temperature of reactions. So essentially you kill-two-birds-with-one-stone.

Some reactions require acidified compounds, and I have even acidified Copper Sulfate to get a typical reaction to occur, but be careful as acidifying solutions can be advantageous but you need to understand the process you are carrying out otherwise this will work in reverse and really screw things up.

Cheers,

Robb.....

[Graham Kemp]

I always add 1ml of conc H2SO4 to my Copper sulfate when I make it up. It stops the yellow precipitate coming out and keeps it a nice blue colour. Not sure what the precipitate is but the acid helps.

The precipitate is copper. Fine particles of copper metal that are reduced out of solution. Acidification helps keep the copper atoms oxidized.

Cu{2+} + 2 OH{-} = Cu (s) + O2 (g) + 2 H{+}

[mtg]

After reading all this I have a sore head. Too early. Need coffee.

[Graham Kemp]

To summarise:

Copper(II) Sulfate is supplied in two forms: Anhydrous and Pentahydrate. The difference is the degree of hydration; the amount of water of crystalisation contained within the crystals. Both form copper sulfate solution, since once disolved they are no longer crystals. If you let the solutions evaporate you will get copper sulfate pentahydrate.

Copper Sulfate Pentahydrate is the deep blue powder or crystals. CuSO4·5H2O has a molecular mass of 249.70 g per mole. Each mole of crystal contains 1 mole of CuSO4 and 5 moles of water. This water is actually contained within the crystal structure.

Copper Sulfate anhydrate is a white powder. CuSO4 has a molecular mass of 159.62 g per mole. The main issue is that anyhdrous copper sulfate is hard to keep anhydrous. It will readily absorb water from the air; pulling it into the crystal latice. The powder turns blue when this happens. As this light-blue powder contains an unknown amount of water you cannot produce a solution of known concentration from it. However the water can easily be driven off by dry heat.

If a concentrated solution is left to stand for any length of time, elemental copper often precipitates out as fine particals that give the solution a greenish colour, or form a yellow stain on the glassware. To prevent this reduction, a small amount of concentrated sulfuric acid is often added during preparation; before the solution is diluted to final volume.

[rae]

Thanks for that Graham.

[Robb]

Hi All,

Back by popular demand is a post which I included on chemtalk a few years ago now.....

This includes adding Sulfuric Acid to Copper Sulfate solution (particularly but not limited to high concentrations). The reason for this sulfuric Additive is to prevent the drop out of Cu2+ and Cu3+ ions which stain the glass/plastic bottle with yellow marks.

The additive needs to be around 1mL of Sulfuric per 500mL of Copper Sulfate.


Apart from that it will keep for a good while....

Cheers,

Robb.....

[mikah]

so it serves a purpose but isn't vital?

[linotas]

There are a couple of pracs our senior chem teacher does that required non acidified copper sulphate so we make ours up without acid as standard. We only add it if asked for acidified coper sulphate. So yes, it's not crucial.

[Robb]

Hi All,

That's right. Only a small amount won't even acidify it when you look at the ratio of Copper sulfate and Sulfuric. It's..... Negligible....

Cheers,

Robb.....

[Robb]

Hi All,

Just retort to my last post.

The pH would not even move by 0.1 pH unit.

Cheers,

Robb.....

[linotas]

Thanks Robb, I have a teacher and job share who are adamant that I cannot use acid in the make up of copper caliphate because of those few experiments. Will maybe mention to them next time.

[Labbie]

just bumping this up as a new member has asked me about it.