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An organic acid containing only C, H, and O has the elemental composition by mass C =...

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lak-86 | Student, Undergraduate | (Level 1) Salutatorian

Posted August 10, 2013 at 4:05 AM via web

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An organic acid containing only C, H, and O has the elemental composition by mass

C = 40.7%

H = 5.1%

Determine the empirical formula of this acid.

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jeew-m | College Teacher | (Level 1) Educator Emeritus

Posted August 10, 2013 at 4:15 AM (Answer #1)

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Molar mass in `g/(mol)`

`C = 12`

`O = 16`

`H = 1`

Percentage mass by material

`C = 40.7`

`H = 5.1`

`O = 100-40.7-5.1 = 54.2`

Let us say we have 100g of the compound. Then we should have 40.7g of C,5.1g of H and 54.2g of O in it.

Amount of `C = 40.7/12 = 3.39`

Amount of `H = 5.1/1 = 5.1`

Amount of `O = 54.2/16=3.39`

`C:H:O = 3.39:5.1:3.39 = 1:5.1/3.39:1 = 1:1.5:1 = 2:3:2`

So the empirical formulae of the compound is `C_2H_3O_2`

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