# Math Help - Chemistry Moles Question

1. ## Chemistry Moles Question

I just had this question on a quiz and I'm not sure what I did wrong.
Question: Calculate the number of hydrogen atoms in 0.125 g of citric acid H3C6H5O7

Heres what I did..
I found the percent composition of hydrogen to be 4.17%, then I found the total moles of hydrogen in citric acid and multiplied it by 0.0417 (this is where I think i went wrong), then multiplied that number by avagadros number to get 1.63 X 10^19 particles.

Anyone care to correct me and provide right answer?

Thanks.

2. Originally Posted by Shout
Question: Calculate the number of hydrogen atoms in 0.125 g of citric acid $C_6H_8O_7$
How did you get 1.63 X 10^19 particles? You have all the working out correct... but not the answer.

First part is correct, 0.125g * 0.0417 = 0.0052125 moles of hydrogen

The next part, you have the method correct, but not the answer.

The Avogadro constant is 6.022×(10^23)

0.0052125 moles * [6.022×(10^23)] = ...

I'm sure you can type that into the calculator yourself?

And you shouldn't get 1.63 X 10^19.