A polystyrene having the formula ${B r}_{3} C_{6} H_{3} {(C_{8} H_{8})}_{n}$ , was prepared by heating styrene with tribromobenzoyl peroxide in the absence of air.

If it was found to contain $10.46 %$ of bromine by mass, the value of $n$ is:

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Solution

% of Bromine = $\frac{mass of Bromine}{mass of compound} \times 100$

Molar mass of $B r_{3} C_{6} H_{2} (C_{8} H_{8}) n$

$= 3 \times 80 + 12 \times 6 + 2 \times 1 + (12 \times 8 + 1 \times 8) n$

$= 314 + 104 n$

$∴ 10.46 = \frac{3 \times 80}{314 + 104 n} \times 100$

$∴ 0.1046 (314 + 104 n) = 240$

$∴ 10.87 n = 240 - 32.84$

$n = 19.05 \approx 19$

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A polystyrene having the formula Br3C6H3(C8H8)n, was prepared by heating styrene with tribromobenzoyl peroxide in the absence of air. If it was found to contain 10.46% of bromine by mass, the value of n is:

% of Bromine = mass of Brominemass of compound×100Molar mass of Br3C6H2(C8H8)n=3×80+12×6+2×1+(12×8+1×8)n=314+104n∴10.46=3×80314+104n×100∴0.1046(314+104n)=240∴10.87n=240−32.84n=19.05≈19

A polystyrene having the formula ${B r}_{3} C_{6} H_{3} {(C_{8} H_{8})}_{n}$ , was prepared by heating styrene with tribromobenzoyl peroxide in the absence of air.

If it was found to contain $10.46 %$ of bromine by mass, the value of $n$ is: