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What does this chemical formula mean?

(14 Posts)
LifeIsGoodish Thu 15-Sep-16 07:32:42


What does the dot in the middle mean?

hellsbells99 Thu 15-Sep-16 07:42:03

It is copper sulfate penthydrate. All it means is that there are 5 water molecules to 1 copper sulfate molecule - the dot is showing it as a ratio

Mrsmorton Thu 15-Sep-16 07:42:42

IIRC it's to do with crystallisation, the ratio of the salt in the crystal is 1:5. One copper sulphate molecule:5 water molecules

LifeIsGoodish Thu 15-Sep-16 16:33:44

So there is no bond? This represents 6 separate molecules, not a single compound?

fuckweasel Thu 15-Sep-16 17:10:11

It's called the water of crystallisation; water molecules in the crystal structure of the copper sulfate. The copper sulfate part is not in molecular form, rather copper ions surrounded by four water molecules which link to sulfate ions (the fifth water molecule exists in the crystal structure but not directly bound to the copper ion).

InTheDessert Thu 15-Sep-16 17:22:15

The water is associated with the copper sulphate. But can be driven off by physical means.
But there is a pretty fixed water to CuSO4 ratio, and are generally found in the crystal lattice together.

TeenAndTween Thu 15-Sep-16 17:29:12

As a matter of interest, what level of Chemistry is this?
I didn't cover it at O level and DD didn't in her double science GCSE, so I would be interested to know if this is C3 GCSE or A level.

Longlost10 Thu 15-Sep-16 17:56:54

Its certainly covered in the BTEC

LifeIsGoodish Thu 15-Sep-16 18:37:13

Thanks! I'm pretty sure I covered this in A-level Chem, but that was 30+y ago!

This GCSE. Ds sat the single award last year, Y10, and is working towards the triple award in Y11.

BizzyFizzy Thu 15-Sep-16 19:11:25

It's blue copper sulfate.

mumsneedwine Thu 15-Sep-16 20:55:03

Can I ask what exam board as I've never seen this on any GCSE - even the new spec. Quite a complex level of understanding of bonding that usually not covered until A2 so would be good to know which board is expecting this now. Thanks

elephantoverthehill Thu 15-Sep-16 21:05:44

I need to go and stand in Pedant's corner. It is SULPHATE! I do hate this new spelling sulfate. Adds nothing to thread except DS1 confirmed about the 5 water molecules and crystallisation stuff.

fuckweasel Thu 15-Sep-16 21:54:58

I need to go and stand in Pedant's corner. It is SULPHATE! I do hate this new spelling sulfate.
The IUPAC (International Union of Pure and Applied Chemists) adopted the 'sulfur' only spelling in 1990. Their nomenclature rules are followed in higher education institutes worldwide and also in English, Scottish and Welsh school examination boards.

Whilst it still pains me to do so (having been taught that 'sulfur' is American and 'sulphur' English) I have gradually also adopted 'sulfur' as if teaching chemistry, it's correct. Spellcheck, however, still disagrees and changes it back to sulphur!

From the Oxford Dictionary: 'The traditional British spelling is sulphur and the US spelling is sulfur. In chemistry and other technical uses, however, the -f- spelling is now the standard form for this and related words in British as well as US contexts, and is increasingly used in general contexts as well'.

elephantoverthehill Thu 15-Sep-16 22:28:09

Oh goodness was it as long ago as 1990? That definitely shows my age.

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