find number of atoms

[crazziekid82]

hello everyone i need help on a question, i have part of it done adn its correct but to get the rest it not working, this is what i have so far

 

Propane is the major LPG constiturnt, assuming that a 17.60g sample is all propane calculate

 

A) number of propane molecules

B) number of carbon atoms

C)number of hydrogen atoms

 

propane= C3H8

 

A) M(c3h8)=44.09gmol-1

n=m/M

= 17.09/44.09

=0.40 moles of propane

 

n=N/6.02x10(23)

N=0.40x 6.02x10(23)

= 2.408x 10(23)

 

B) n©=N/6.02x10(23)

= 12.01x 6.02x10(23)

= 7.23x10(24) .. the answer says 7.22x10(23) which im not sure what i am doing wrong

 

and i can not get the correct answer for hydrogen, final answer is 1.93 x 10(24)

 

please help with the working out.

[Klaynos]

I think you're over thinking it.

 

How many atoms are there per molecule?

 

Then just times that by the number of molecules.

[insane_alien]

why have you used 17.09g as the mass of propane and not 17.60g like the question says?

 

and the errors you are getting look like simple rounding errors, try using more significant figures.

[Imaginer1]

I agree with insane alien- and I'm pretty sure

C3H8

would be carbon three atoms, hydrogen eight atoms. I don't really see those numbers.

 

P.S. I could be wrong. I'm eleven. I just am more advanced than most

[insane_alien]

carbon 3? thats an impossible isotope. what you should have got from that was, 3 carbon atoms and 8 hydrogen atoms.

[Imaginer1]

DONT BLAME ME IM ELEVEN!

(runs away)

[insane_alien]

dude, chill, i wasn't blaming anyone. just correcting a little mistake.

[crazziekid82]

why have you used 17.09g as the mass of propane and not 17.60g like the question says?

 

that was a typing error the answer is still the same.