Question

An organic compound contains C=52%,H=8.5% and O=39.5%. its mfm is 88 gram per mole.Calculate the empirical formula and molecular formula

Answer 1

Answer:

C4 H8 O

Explanation:

One strategy to use when given the molar mass of the compound is to pick a sample that would correspond to one mole and use it to find the molecular formula without finding the empirical formula first.

In this case, a molar mass of  88g mol − 1

tells you that one mole of this compound has a mass of  88 g .

Use the percent composition of the compound to determine how many grams of each element you'd get in this  

88-g

sample. Remember, you can convert between percentages and grams by using a sample of  100 g .

You will thus have

For C:  

88  g sample ⋅

54.53 g C

100 g sample = 47.986 g C

For H:  

88 g sample ⋅

9.15 g H

100 g sample = 8.052 g H

For O:  

88 g sample ⋅ 36.32 g O

100 g sample = 31.962 g O

Now use the molar mass of each element to determine how many moles of each are present in one mole of this compound

For C:  

47.986 g ⋅

1 mole C  12.011 g = 3.995 ≈ 4 moles C

For H:  

8.052 g ⋅

1 mole H  1.00794 g = 7.990 ≈ 8 moles H

For O:

 31.962 g ⋅

1 mole O 15.9994 g = 1.998 ≈ 2 moles O

Since this is how many moles of each element are present in one mole of this compound, you can say that one molecule of the compound will contain

4  atoms of carbon

8  atoms of hydrogen

2  atoms of oxygen

Therefore, the compound's molecular formula, which tells you exactly how many atoms of each element make up one molecule of the compound, will be  C 4  H 8  O 2