finding molecular formulas from empirical

[906430805]

At what point when calculating an empirical formula should you round up to the next whole number, and at what value should you choose instead to multiply by another number to get to whole numbers.

For instance, if I found that the ratio in a Hydrocarbon between C and H was 2:4.8, can I round up to 2:5?

And how much should I factor in how well my imperical weight factors into the overall molar mass?

For instance, if I am told that the molar mass of the above hydrocarbon is 216g, then the empirical formula above doesn't divide in very well.

[AnnaKessler2C]

I had a UA tell me that if its less than .3 you can round down and more than .7 you can round up. for that .3-.7 space you have to multiply to find a whole number.

For instance, if I found that the ratio in a Hydrocarbon between C and H was 2:4.8, can I round up to 2:5? - Yes

And how much should I factor in how well my empirical weight factors into the overall molar mass?

For instance, if I am told that the molar mass of the above hydrocarbon is 216g, then the empirical formula above doesn't divide in very well. - I think on the exam we will get numbers that leave us without question.