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### Topic: easy peasy lemon squeezy. apparently!  (Read 3912 times)

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#### ellis182

• Guest
##### easy peasy lemon squeezy. apparently!
« on: March 16, 2005, 03:44:40 AM »
Guys just a really easy question i need clarification with..

How many moles of O-atoms in 25.7g of CaSO4?

I know moles = mass/molar mass

so..

25.7/(40.8 + 32.07 + 4x16) = .188

Is this the answer or do i multiply .188 by 4 because there is 4 oxygen atoms in CaSO4?

Also..

How many molecules in 13.72g oh hydrazine? N2H4? i dont even know where to start!

If anyone could help me at all it would be much appreciated!

#### Borek

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##### Re:easy peasy lemon squeezy. apparently!
« Reply #1 on: March 16, 2005, 05:10:01 AM »
25.7/(40.8 + 32.07 + 4x16) = .188

Is this the answer or do i multiply .188 by 4 because there is 4 oxygen atoms in CaSO4?

Quote
How many molecules in 13.72g oh hydrazine? N2H4? i dont even know where to start!

Hydrazine is like every other substance. Just calculate molar mass of N2H4, rest is obvious.
ChemBuddy chemical calculators - stoichiometry, pH, concentration, buffer preparation, titrations.info, pH-meter.info

#### mPeppel

• Guest
##### Re:easy peasy lemon squeezy. apparently!
« Reply #2 on: March 18, 2005, 12:00:12 PM »
13.72g N2H2/ 30.04gN2H2  =  0.4567moles
0.4567moles x 6.022 x10 23 molecules/ 1moles =2.750 x10  23 molecules