A certain combustion reaction generates 0.500 moles of carbon dioxide. How many grams does this represent? Report your answer to 3 significant figures. g

Answer 1

molar mass CO2 = 44.0 g/mol

0.500 mol CO2 x 44.0 g / mole = 22.0 g CO2

Answer 2

I like to start all of my problems by looking at what I know and what I don't.

I know:

I have 0.500 moles of Carbon Dioxide (CO2)

I don't know:

The Molar Mass of CO2

How many grams of CO2 I have

This kind of question is pretty common and it can be a little hard because it doesn't give you a lot to work with. You don't get any other reagents or even a chemical formula but you really don't need it.

First you will have to figure out the molar mass of CO2 using a Periodic Table

EX: The Molar Mass of Ammonia (NH3)

Molar Mass of Nitrogen (N) is about 14 and there is 1 atom per molecule

Molar Mass of Hydrogen (H) is about 1 and there are 3 atoms per molecule

Molar Mass of Ammonia = (1x14)+(3x1) which is about 17 grams per mole (You can use more significant figures when you do your work)

Next you can determine how many grams of substance you have.

EX: If you have 2 moles of NH3 you can convert that number of grams

2 Moles x (17 grams / mole) = 34 grams of Ammonia

Remember that the moles cancel out and you are left with only grams