# chemistry

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How many moles of sugar are required to react completely with 3.26 mol of oxygen?

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Write the equation and balance it, then follow the instructions on the link I'm giving you. I'll help by giving you the balanced equation.
C12H22O11 + 12O2 ==>12CO2 + 11H2O

http://www.jiskha.com/science/chemistry/stoichiometry.html
This link will work any stoichiometry problem you have.

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_____C2H5OH +_____ O2 „_ _____CO2 + _____H2O

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Convert 3.09 g PCl5 to molecules

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Find the percent by mass of oxygen in CaCO3

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You should post separate questions for these, otherwise they sometimes get left behind.
C2H5OH + 3O2 ==> 2CO2 + 3H2O

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%oxygen = (mass Oxygen/molar mass CaCO3)*100 = ?
mass oxygen, use atomic mass O or 3*16 = ?

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moles PCl5 = grams/molar mass.
Then remember there are 6.022E23 molecules in one (1) mole of anything.

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Calculate the mass of 3.53 x 10^12 atoms of gold is it 6.95x10^14?!

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Convert 3.09 g PCl5 to molecules im getting two differnt answers when I'm doing this kind of problems I got .015mol than 14.82mol which is correct?

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What is the mass of 4.419 mol of potassium nitride?

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These are the last questions I will answer to this post. Post a new question if you have one.
moles Au = (3.53E12/6.022E23), then moles x atomic mass Au = grams Au. 6.95E14 is not correct.

For molecules PCl5 you would have done better to show what you did and I could find the error. It's more important to know how to work the problem.
moles = grams/molar mass = 3.09g/208.2 = 0.0148 (you have three places in 3.09 so DON'T round to 0.015) and moles x 6.022E23 = 8.94E21.

K3N problem.
grams = moles x molar mass
g = 4.419 x molar mass K3N = ??