PLZZ ANSWER ....A sample of polystyrene is prepared by heating styrene with tribromobenzoyl peroxide in the absence of air has the formula Br3C6H3 (C8H8)n. A sample of polystyrene prepared in this manner was found to contain 12% of bromine. The value of n in the formula is:
1) 12
2) 16
3) 19
4) 18
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Answer:
b) 45
Explanation:
Constituency of bromine = 10.46%
Let the weight of polystyrene prepared = 100 g
Thus, the number of moles of Br in 100g of ploystyrene
= 10.46 / 79.9
= 0.1309
Formula of polystyrene - Br3,C6H3 - from the formula of polystyrene -
Number of moles of Br = 3 × number of moles of Br3C6H3(C8H8)n
= 0.1309 = 3 × Wt / molar weight
= 0.1309 = 3 × 100 / (314.7 + 44n)
= 0.1309 × ( 314.7 + 44n ) = 300
= 2291.825 = (314.7 + 44n)
= 44n = 2291.825 - 314.7
n = 1977.1/44
n = 44.93
n = 45 (approx)
Therefore value of n is 45.
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