Question

3. Vitamin C contains the elements C, H, and O. It is known to contain 40.9% C and 4.58% H and 54.52% O by mass. The molar mass of vitamin C has been found to be about 180.0 g/mol. Find the: a) empirical formula and b) molecular formula of Vitamin C.

Answer 1

a)

we have mass of each elements as:

C: 40.9 g

H: 4.58 g

O: 54.52 g

Divide by molar mass to get number of moles of each:

C: 40.9/12.01 = 3.4055

H: 4.58/1.008 = 4.5437

O: 54.52/16.0 = 3.4075

Divide by smallest:

C: 3.4055/3.4055 = 1

H: 4.5437/3.4055 = 4/3

O: 3.4075/3.4055 = 1

Multiply by 3 to get simplest whole number ratio:

C: 1*3 = 3

H: 4/3 * 3 = 4

O: 1*3 = 3

  

So empirical formula is:C3H4O3

b)

Molar mass of C3H4O3,

MM = 3*MM(C) + 4*MM(H) + 3*MM(O)

= 3*12.01 + 4*1.008 + 3*16.0

= 88.062 g/mol

Now we have:

Molar mass = 180.0 g/mol

Empirical formula mass = 88.062 g/mol

Multiplying factor = molar mass / empirical formula mass

= 180.0/88.062

= 2

So molecular formula is:C6H8O6