x Turn on thread page Beta
 You are Here: Home

# Molar Ratios watch

1. QUESTION:
"A sample of verdigris has the formula [(CH3COO)2Cu]2.Cu(OH)2.xH2O.
Analysis of the sample shows that it contains 16.3% water by mass.
Calculate the value of x in the formula."

I Know Mr of [Cu(CH3COO)2]2.Cu(OH)2 = 460.5

What Next?
2. Find X

(460.5/X) x 100 = 100 - 16.3

then use that molar mass to calculate the number of waters
3. (Original post by EierVonSatan)
Find X

(460.5/X) x 100 = 100 - 16.3

then use that molar mass to calculate the number of waters
Pure Genius ,

I found difficulty incorporating the 16.3% into the method - but you just hit the hammer directly on the nail!

Ever Grateful, qazwsxedc
4. (Original post by qazwsxedc)
Pure Genius ,

I found difficulty incorporating the 16.3% into the method - but you just hit the hammer directly on the nail!

Ever Grateful, qazwsxedc
anytime
5. (Original post by EierVonSatan)
anytime

I've only started AS chemistry, but could you not do an empirical formula, calculation, but using percentages instead of mass? Or does the fact that it's organic mean that wouldn't work?
6. (Original post by DaveJ)
I've only started AS chemistry, but could you not do an empirical formula, calculation, but using percentages instead of mass? Or does the fact that it's organic mean that wouldn't work?
No I don't think so - if I think I know what you're suggesting - i.e. do it by element (Cu is 25%, O is 16%, H is 5% by mass?)
7. (Original post by EierVonSatan)
No I don't think so - if I think I know what you're suggesting - i.e. do it by element (Cu is 25%, O is 16%, H is 5% by mass?)
QUESTION:
"A sample of verdigris has the formula [(CH3COO)2Cu]2.Cu(OH)2.xH2O.
Analysis of the sample shows that it contains 16.3% water by mass.
Calculate the value of x in the formula."

I Know Mr of [Cu(CH3COO)2]2.Cu(OH)2 = 460.5

What Next?

Not really. I mean, you know 16.3% is water, so 83.7% isn't water.

Divide 16.3 by 18 to get moles of water, and divide 83.7 by 460.5 (I think the 460.5 doesn't include the Mr of water) to get the moles of everything else.

Then simpify the ratio?
8. (Original post by DaveJ)
Not really. I mean, you know 16.3% is water, so 83.7% isn't water.

Divide 16.3 by 18 to get moles of water, and divide 83.7 by 460.5 (I think the 460.5 doesn't include the Mr of water) to get the moles of everything else.

Then simpify the ratio?
Lets try it:

16.3/18 = 0.9056
83.7/460.5 = 0.1817

divide by the lowest number

H2O: 4.98
[Cu(CH3COO)2]2.Cu(OH)2: 1

so yeah that does work
9. (Original post by EierVonSatan)
Lets try it:

16.3/18 = 0.9056
83.7/460.5 = 0.1817

divide by the lowest number

H2O: 4.98
[Cu(CH3COO)2]2.Cu(OH)2: 1

so yeah that does work
OK, thanks!

TSR Support Team

We have a brilliant team of more than 60 Support Team members looking after discussions on The Student Room, helping to make it a fun, safe and useful place to hang out.

This forum is supported by:
Updated: November 9, 2008
Today on TSR

### Any tips for freshers...

who are introverts?

### More snow?!

Discussions on TSR

• Latest
Poll
Discussions on TSR

• Latest

The Student Room, Get Revising and Marked by Teachers are trading names of The Student Room Group Ltd.

Register Number: 04666380 (England and Wales), VAT No. 806 8067 22 Registered Office: International House, Queens Road, Brighton, BN1 3XE