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Answered

A 0.00215-g sample of polystyrene, a polymer composed of carbon and hydrogen, produced 0.00726 g of CO2 and 0.00148 g of H2O in a combustion analysis. What is the empirical formula for polystyrene?

Answer :

Maacastrobrgo

Answer:

CH

Explanation:

Polystyrene is composed only by C and H.

We can calculate the number of C moles contained in the original sample mass (0.00215 g), using the produced mass of CO₂:

  • 0.00726 g CO₂ ÷ 44 g/mol = 1.65x10⁻⁴ mol CO₂

As 1.65x10⁻⁴ moles of CO₂ were produced, in the polystyrene sample there were 1.65x10⁻⁴ moles of C.

Now we calculate how many moles of H₂O were produced:

  • 0.00148 g H₂O ÷ 18 g/mol = 8.22x10⁻⁵ mol H₂O

The number of H moles produced is double the amount of H₂O moles, so in the polystyrene sample there were 1.64x10⁻⁴ moles of H.

The number of C and H moles are the same, this means the empirical formula is CH.

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