Chemistry questions? amu and moles...
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Chemistry questions? amu and moles...

[From: ] [author: ] [Date: 12-09-28] [Hit: ]
-whats the mass of this sample in grams?Give the empirical formula for 17.37 g C, 4.37 g H, and 0.......
i'm doing homework and these are the problems that are stumping me. Any one help?

balance:
__CH3NH2+__O2--->__CO2+__H2O+__N2

__C3H6+__O2--> __CO2+__H2O

Please explain how you did the following so i can figure out the rest of my homework!

A sample of glucose, C6H12O6, contains 1.247 x 10^21 atoms of carbon.
-how many atoms of hydrogen does it contain?
-how many molecules of glucose?
-how many moles of glucose?
-what's the mass of this sample in grams?

Give the empirical formula for 17.37 g C, 4.37 g H, and 0.0333 mol O

If 0.273 g of Mg is reacted with nitrogen, 0.378 g of the4 nitride is formed. determine the empirical formula of the compound.

-
balance:

2CH3NH2+ 3O2--->2CO2+ 2H2O+N2

this one you just have to find a common number. So i started by seeing there was only 1 N in CH3NH2 and 2 N in the products. So you have to put a 2 in front of CH3NH2. Then you continue from there making sure there are the same number of elements in both the reactants and products.

C3H6 + 4.5 O2--> 3CO2 + 3H2O
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A sample of glucose, C6H12O6, contains 1.247 x 10^21 atoms of carbon.

1) How many atoms of hydrogen does it contain.

Well looking at the chemical formula of glucose you see that the ratio of carbon to hydrogen is 1:2, meaning there are twice the number of hydrogen atoms to carbon. Therefore, since you know that there are 1.247 x 10^21 atoms of carbon there is twice the number of hydrogen atoms, 2.494x10^21.

2) how many molecules of glucose?

Similarly you know that there are 6 carbon atoms in each glucose molecule. So if there are 1.247 x 10^21 atoms of carbon there are (1.247 x 10^21 divided by 6) 2.078 x 10^20 molecules of glucose.

3) how many moles of glucose?

For this on one mol is 6.02x10^23. So there are 6.02x10^23 molecules/mole.

So 2.078 x 10^20 molecules of glucose / 6.02x10^23 molecules/mol (the molecules cancel out this way) and the answer is 3.451x10^-4 moles of glucose.

4) what's the mass of this sample in grams?

The molar mass of glucose is:
C--> the molar mass is 12.01 g/mol and there are 6 atoms therefore it will be 72.06 g/mol
H --> 1.01 g/mol x 12 = 12.01g/mol
0--> 16g/mol x 6 = 96 g/mol
therefore the molar mass of glucose is 180.07g/mol. Now you know that there is 3.451x10^-4 moles of glucose, thereofore the mass of glucose is (180.07g/mol x 3.451x10^-4 moles) =0.0621g.
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SOrry I ran out of time but I wanted to post those first two for now. If i come back and no one has helped with the rest I will post the answers.
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