A polystyrene having formula $B r_{3} C_{6} H_{3} (C_{3} H_{8})_{n}$ found to contain 10.46% of bromine by weight. Find the value of $n$ .
(Atomic weight $B r = 80$ )

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Solution

The correct option is A 45
One molecule of polystyrene $= 3$ Bromine atom

$10.46$ % Bromine by weight means $= \frac{m a s s o f B r o m i n e a t o m s}{m a s s o f m o l e c u l e}$

$\frac{10.46}{100} = \frac{3 \times 80}{3 \times 80 + 75 + 44 n}$

$10.46 (315 + 44 n) = 3 \times 80 \times 100$

$3294.9 + 460.24 n = 3 \times 80 \times 100$

$460.24 n = 24000 - 3294.9$

$n = 44.988$

$n ≅ 45$

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Similar questions

{B r}_{3} C_{6} H_{3} {(C_{8} H_{8})}_{n}

10.46 %

n

C_{3} H_{6}

1.0 g

8.89 g

80

12.8

2.1

85.1

187.9

H = 1.008, C = 12.0, B r = 79.9

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