Question

Salicylic acid, used in the synthesis of as- pirin, has mass composition 60.87% C, 4.38% H, and 34.75% O. What is the empirical for- mula of the compound?

Answer 1

Answer: Empirical formula is
`C_2H_(2)O`

Step-by-step explanation:

If percentage are given then we are taking total mass is 100 grams.

So, the mass of each element is equal to the percentage given.

Mass of C= 60.87 g

Mas of H = 4.38 g

Mass of O = 34.75 g

Step 1 : convert given masses into moles.

Mass of C =
`\frac{\text{ given mass of C}}{\text{ molar mass of C}}= (60.87g)/(12g/mole)=5.07moles`

Moles of H =
`\frac{\text{ given mass of N}}{\text{ molar mass of N}}= (4.38g)/(1g/mole)=4.38moles`

Moles of O=
`\frac{\text{ given mass of O}}{\text{ molar mass of O}}= (34.75g)/(16g/mole)=2.17moles`

Step 2 : For the mole ratio, divide each value of moles by the smallest number of moles calculated.

For C =
`(5.07)/(2.17)=2`

For H =
`(4.38)/(2.17)=2`

For O =
`(2.17)/(2.17)=1`

The ratio of C:H:O= 2 : 2: 1

Hence the empirical formula is
`C_2H_(2)O`