Do you need the .0? And a molar mass question

[excelsiorxlcr]

Hi there!
When you have a number you are using in a calculation which ends in .0 (or .00 or .000, etc), such as the molar mass of water which is 18.0, is it essential to carry the '.0' in your calculations? Most of the time I don't bother adding the zeros at the end, but I am wondering if doing this could ever give me a different answer to what I would get if I added .0 to the end.

I also have a random question about molar mass. When you are finding the molar mass of a substance that exists as more than one molecule, do you find the molar mass of just one of those molecules, or all of them? eg: is the molar mass of oxygen M(O2) or simply M(O)?

Thanks in advance!

[blacksanta62]

Hey
The .0 actually doesn't affect your calculations. Any whole number you see, such as 100, or 4376 etc. can be 100.0 or 100.00, similarly, it can be 4376.0 or 4376.00. But we don't write them like that because they are the same thing and you don't need to add them on while doing your calculations. However, decimals like 2.396539...3234 etc, use them in that form while doing calculations but round them to the correct number of significant figures and in your final answer. 

With your second question, find the molar mass of the substance they give you. Oxygen, only exists as O₂(g), so with that example, the M is all of the molecules atoms, not just one.

Hope I helped