Could someone check my chemistry about moles & masses.

I have a quiz over these problems tomorrow different ones i was wondering if i did this right...

Are these correct?

Find the mass of 5.0 moles of phosphorus

(30.97g) x (5.0 moles) =153.5 grams

find the mass of 4.0 moles of zinc

(65.38g) x (4.0 moles) = 261.52 grams

find the mass of 5 moles of water (H2O) i got 72.064 grams as i found the atomic weight for both hydrogen and oxygen and combined them.

How many moles of lithium are in a 10.0 gram sample of lithium?
I got: number of moles of Li=10.0/6.9=1.45 mol.

How many moles of Aluminum are in a 100 gram sample of aluminum? I got: number of moles of Al=100/27.0=3.70 mol.

Determine the percentage composition (by mass) of C2H6O I got:

Total Mr = 12.0x2 + 1.0x6 + 16.0 = 46.0
% by mass of carbon = 2x12.0/46.0 x 100% = 52.2%
% by mass of hydrogen = 1.0x6/46.0 x 100% = 13.0%
% by mass of oxygen = 16.0/46.0 x 100% = 34.8%


And by any chance...if anyone has time can they help me do these and show me the work on how its done? I would much appreciate it.

What is the formula weight of BaCl2?

How many grams of BaCl2 (see problem 5) would be in 3 moles of BaCl2?

Thank-you so much.

 

Based on my guestimate math, this appears to be wrong.

18g X 5 ~ 90.

Uh...

Mass of BA + 2 X Mass of CL

That number X 3...

 

I dont get what your saying...is that the formula weight...?

Mass of BA + 2 X Mass of CL???

And that number X 3?

What do you mean..

 

He means exactly what he said - The formula weight of BaCl2 is indeed that number.

Then to find how many grams of BaCl2 there are in three moles, multiply the aforementioned number by three.

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Stoichiometry is quite easy once you get used to it really. The most confusing part is finding the amount of a product of a reaction, or at least that's what I found to be confusing when I first did it.