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Chemistry Forums for Students => High School Chemistry Forum => Topic started by: alexs0fly on September 10, 2007, 08:07:01 PM

Title: How many H atoms are present in a 2.00 g sample of styrene?
Post by: alexs0fly on September 10, 2007, 08:07:01 PM
"The emperical formula of styrene is CH. The molar mass of styrene is 104.14 g/mol. How many H atoms are present in a 2.00 g sample of styrene?"

I've already got the molecular formula - C8H8 but idk where to go from here. I know there are 6.02x10^23 particles of 1 mol of anything. And there are 8 moles of H right? Where does the 2.00g come into play?
Title: Re: Help
Post by: Yggdrasil on September 10, 2007, 08:10:30 PM
How many moles of styrene are in 2.00g?
Title: Re: Help
Post by: alexs0fly on September 10, 2007, 08:18:45 PM
.0192
Title: Re: Help
Post by: Borek on September 11, 2007, 02:47:06 AM
How many styrene molecules per 0.0192 mole of styrene?

How many hydrogen atoms per styrene molecule?

Note: where did you get the C8H8 formula from? It is correct, but it should be calculated from the data given in the question.
Title: Re: Help
Post by: AWK on September 11, 2007, 03:18:39 AM
Molecular mass and formula are not needed in your calculations.
Calculate mass fraction of H in your empirical formula (~1/13), then multiply it by a mass of your sample (~2/13) - this is the mass of hydrogen in your sample. Then convert it to moles of atoms, and finally to a number of hydrogen atoms