Question

An organic compound with the molar mass of 180 g/mol contains 40% C, 6.67% H and 53.33% O by mass. Find its molecular formula.
* please, write your calculations, not only answer
i hope that you help me

Answer 1

Answer:

In 100 g of the unknown, there are

40.0

⋅

g

12.011

⋅

g

⋅

m

o

l

−

1

C

;

6.7

⋅

g

1.00794

⋅

g

⋅

m

o

l

−

1

H

; and

53.5

⋅

g

16.00

⋅

g

⋅

m

o

l

−

1

O

.

We divide thru to get,

C

:

H

:

O

=

3.33

:

6.65

:

3.34

. When we divide each elemental ratio by the LOWEST number, we get an empirical formula of

C

H

2

O

, i.e. near enough to WHOLE numbers.

Now the molecular formula is always a multiple of the empirical formula; i.e.

(

EF

)

n

=

MF

.

So

60.0

⋅

g

⋅

m

o

l

−

1

=

n

×

(

12.011

+

2

×

1.00794

+

16.00

)

g

⋅

m

o

l

−

1

.

Clearly

n

=

2

, and the molecular formula is

2

×

(

C

H

2

O

)

=

C

x

H

y

O

z

.