Question

Calculate the empirical formula of a compound that is 85.6% carbon and 14.4% hydrogen.

Answer 1

Answer:

AS with all these problems, we assume (for simplicity)

100

⋅

g

of unknown compound.

And thus there are

85.7

%

×

100

⋅

g

12.011

⋅

g

⋅

m

o

l

−

1

with respect to carbon, i.e.

7.14

⋅

m

o

l

⋅

C

And

14.3

%

×

100

⋅

g

1.00794

⋅

g

⋅

m

o

l

−

1

with respect to hydrogen, i.e.

14.1

⋅

m

o

l

⋅

H

.

And thus the

empirical formula

, the simplest whole number ratio that defines constituent elements in a species is

C

H

2

.

Now the

molecular formula

is alway a whole number multiple of the

empirical formula

:

empirical formula

×

n

=

molecular formula

So

(

12.011

⋅

g

⋅

m

o

l

−

1

+

2

×

1.00794

⋅

g

⋅

m

o

l

−

1

)

×

n

=

84

⋅

g

⋅

m

o

l

−

1

.

So

n

=

6

, and

molecular formula

=

6

×

C

H

2

=

C

6

H

12