What is the mass of oxygen in 7.38 g of carbon dioxide?

Answer 1

It's all about ratios and moles.

In 44g of CO2 32g is oxygen (2x16) and 12g is carbon (12). We can show that as a fraction 32/44 is oxygen.

Your question asks for the mass of oxygen in 7.38g. Lets call the mass x (I love algebra). We are looking for a mass, x, out of 7.38 and we know how the ratios work in another example. So we can say:

x/7.38 = 32/44

Or, in English, if 32 out of 44 is oxygen, how much oxygen is in 7.38?

We need to rearrange the equation to get x on it's own...

x/7.38 = 32/44

x = 32/44 *7.38

x= 5.37g

It's difficult to explain it on the internet. If you still don't get it then please talk to your teacher. It's their job to explain it!