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A 10.00 g sample of a compound containing C, H, and O is burned completely to produce...

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lak-86 | Student, Undergraduate | Salutatorian

Posted August 10, 2013 at 4:08 AM via web

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A 10.00 g sample of a compound containing C, H, and O is burned completely to produce 14.67 g of CO2 and 6.000 g of H2O. What is the empirical formula of this compound?

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

Posted August 10, 2013 at 4:43 AM (Answer #1)

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Let us say the empirical formulae of the acid is `C_xH_yO` .

`C_xH_yO +(x+y/2-1)O_2 rarr xCO_2+(y/2)H_2O`

Molar mass in `g/(mol)`

`C = 12`

`H = 1`

`O = 16`

`CO_2 = 44`

`H_2O = 18`

Amount of `CO_2` produced `= 14.67/44 = 0.333`

Amount of `H_2O` produced `= 6/18 = 0.333`

Let us say we have n moles of the compound.

Molar ratio

`C_xH_yO:CO_2 = 1:x`

1:x = n:0.333

`x = 0.333/n = 1/(3n)`

`C_xH_yO:H_2O = 1:y/2`

`1:y/2 = n:0.333`

`y = 2/(3n)`

It is given that the mass of the compound was 10g.

`n(12x+1y+16) = 10`

`n((12/(3n))+2/(3n)+16) = 10`

`4+2/3+16n = 10`

`n = 16/3`

`x = 1/16`

`y = 1/8`

`C:H = 1/16:1/8 = 1:2`

So the empirical formulae would be `CH_2O`

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