Question

A compound is 80% carbon and 20% hydrogen by mass, and has a molecular weight of 30.0 g/mol. determine the molecular formula

Answer 1

Do you know how to find empirical formula?

Answer 2

@Abmon98 =_= don't u dare tell everything

Answer 3

let the asker think and try figuring out first

Answer 4

yes empirical formula is the lowest ratio of a molecular formula

Answer 5

okay
can you do that here?

Answer 6

the 30.0 g/mol is what is really messing me up on approaching it

Answer 7

no this is not yet

Answer 8

first it this
percentages here can be considered to be 'mass'
so you have mass, and you do know Mr of carbon and hydrogen atom
so you can use mole formula

Answer 9

u can find mole of H and C

Answer 10

can you do that?

Answer 11

so 80 g C and 20 g H. so like 6ish mol C and 20 mol H. So the formula would be CH3?

Answer 12

no, wrong

Answer 13

your way of thinking is right

Answer 14

but the mole you get, you cannot round of

Answer 15

well im trying to do this for standard testing so trying to not use a calc

Answer 16

80/12= 6.666666667 moles
20/1= 20 moles
remember that you have to divide both moles by the smallest

Answer 17

oh well then it's okay i guess

Answer 18

o maybe i shoulda rounded up for the carbon?

Answer 19

oh btw lol u did it right

Answer 20

o ok

Answer 21

no its just when you find the moles, do not round them of and straightaway divide by the smallest

Answer 22

it'll give you greater accuracy

Answer 23

but yeah empirical formula is going to be CH3 as you said

Answer 24

ok

Answer 25

can you figure what to do next?

Answer 26

CH3 is like 15 g? so since it is 30.0 g it would be double?

so C2H6?

Answer 27

good job!!

Answer 28

but 15 is not gram its g/mole which is Mr

Answer 29

do not confuse it with gram which is mass

Answer 30

o my bad

Answer 31

ye ok ty

Answer 32

:D hope you understand now :)