[positiveion]

How many atoms of oxygen are there in 500g of Roundup?

Roundup is C3H8NO5P and has a molar mass of 169

The answer is 8.91x10^24 but I don't know how to get that


My attempt at working it out is:

There are 18 atoms in roundup, so 500/18 = 27.77778

That multiplied by 5 (the no. atoms of oxygen) is 138.8888889

Which is obviously wrong

So how would I figure out the accurate answer?

[UG]

There are 18 atoms in roundup

Where did you get that information from?
Have you heard of the mole? Or Avagadro's number?
You obviously know what it is since it's in the title
First you gotta work out the number of moles of C₃H₈NO₅P
Then, find out the moles of oxygen, it's a 1 : 5 ratio and then multiply by the avagadro number

[positiveion]

Um okay I made a mistake..

So how would I do the problem, then?

[UG]

First you gotta work out the number of moles of C3H8NO5P, ie=mass/molar mass
Then, find out the moles of oxygen, it's a 1 : 5 ratio and then multiply by the avagadro number

[Borek]

There are 18 atoms in roundup

That's OK - but you don't need this information, and for sure whatever you did with it was wrong.

Bsides, you will need only information about number of atoms of oxygen.