A polystyrene, having formula Br3,C6H3,(C3H8)n was prepared by heating

1.	A polystyrene, having formula Br3,C6H3,(C3H8)n was prepared by heating styrene with tribromobenzoylperoxide in the absence of air. If it was found to contain 10.46% bromine by weight, the value of n is(A) 19(B) 45(C) 38(D) 56
Answer» 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.

A polystyrene, having formula Br3,C6H3,(C3H8)n was prepared by heating styrene with tribromobenzoylperoxide in the absence of air. If it was found to contain 10.46% bromine by weight, the value of n is(A) 19(B) 45(C) 38(D) 56

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.