Question

the emperical formula if a compound CH and its vapour density is 39 and find its molecular formula?when C=12 and H=1​

Answer 1

Explanation:

For this kind of problem, you can assume that the weight of the unknown sample is 100g ( since 75%

C

+ 25%

H

= 100%).

Thus,

weight of

C

= 75g

weight of

H

= 25g

Since chemical formulas deal with number of moles rather than weight in grams, you need to convert each element by multiplying it to their respective atomic masses.

atomic mass of

C

=

12.01

g

mol

atomic mass of

H

=

1.01

g

mol

Thus,

mol

C

= 75

grams

x

1 mol

12.01

grams

= 6.245 mol

C

mol

H

= 25

grams

x

1 mol

1.01

grams

= 24.752 mol

H

Now we can see from the computation above that every

6.245 mol

C

= 24.752 mol

H

Dividing both sides by the smallest number of moles, (in this case 6.245 mol

C

)

C

=

6.245

mol

6.245

mol

= 1

H

=

24.752

mol

6.245

mol

= 3.98

≈

4