Homework Help :) Two Chemistry Questions involving diatomic elements anyone?

Question

Thanks for reading this...I think I know how, but need a little reinforcement.
1) How many molecules are contained in 6.53 mol of nitrogen gas N2?
2) A sample of oxygin gas O2, weighs 28.4 g. How many molecules of O2, and how may atoms of O are present in this sample?
Thank you

Wow, thanks for the comprehensive answers guys! ~cheers

Answer 1

Moles multiplied by 6.02 times 10 raised to the 23 power is the number of molecules.
Nitrogen, Oxygen, Hydrogen, Chlorine, Argon etc, all gas molecules travel in covalently bonded pairs N2, O2, H2, Cl2,Ar2.

The question states 6.53 Mol of Nitrogen "gas". So being a gas, the Mol in this case refers to "molecules" of "gas" N2 (not atoms of individual Nitrogen atoms).

Ans: There are 6.53 * 6.02*(10**23) molecules of N2 gas.
( 6.02 multiplied by 100000000000000000000000 ( 23 zeros) )
=3.93106E+24 molecules N2
Round to 3 significant digits, because the 6.53 was given with 3 significant digits.

Ans: =3.93E+24
- - - - -
Oxygen has a mass of 28.4g. How many molecules, and how many atoms.
Look on the periodic chart, and find ( atomic weight) how many grams per mole of Oxygen ( individual Oxygen atoms, not pairs).

Use the link below, then click on Oxygen O, shows the Atomic Weight is 15.9994. Round this up to 16.

So Oxygen atoms have 16 grams for one mole ( of atoms).
How many Moles of Oxygen do you have?
Multiply or divide grams, and grams per mole arranged so that the units cancle out leaving the units that you want. ( Moles)
So grams divided by grams per Mole, ( grams cancle from top and bottom leaving Moles).

How many Oxygen atoms are present in the sample:
28.4g /(16 g /Mole )=1.775 Moles Oxygen "atoms".
Multiply by 6.02^23 to convert Moles to atoms.
1.775 * 6.02^23 = 1.06855/e+24 rounded to 3 significant digits
Ans= 1.07E24 atoms

How many Molecules? Oxygen travels in pairs, so divide the number of atoms by 2.
Ans: = 5.34E23 Molecules O2

Austin Semiconductor

Answer 2

For any compound with any formulat, if you multiply the number of moles in a sample by Avogadro's number (6.023 X 10^23) you have calculated the number of molecules in the sample.

For the second one, if you take the mass and divide it by the molecular weight of O2 (32.0 grams/mole) that gives you the number of moles of O2 in the sample. If you multiply that by Avogadro's number that gives you the number of molecules. Now, each molecule of oxygen (O2) contains two oxygen atoms. So, if you multiply the number of molecules by 2, you have the number of oxygen atoms in the sample.

Hope this helps...

Answer 3

theres 6.23x10^23 molecules in a mole.. so

1) 6.53x6.02x10^23 = answer

2) 28.4g/32g= .8875 moles O2; molecules and atoms are the same amount... (32g = 2 parts O2, 16g each on per. table)

.8875x6.02x10^23 =answer

Answer 4

Thank you for reading this I think I know how to solve this i need a little guide only. in 1.008g of hydrogen there are 6.23x10^23 atoms. What is the mass of one atom of hydrogen? thank you.