JEE MAIN - Chemistry (2022 - 30th June Morning Shift - No. 7)
A $$\mathrel{\mathop{\kern0pt\longrightarrow} \limits_{}^{573\,K}} $$ Red phosphorus $$\mathrel{\mathop{\kern0pt\longrightarrow} \limits_{under\,pressure}^{heat\,;\,803\,K}} $$ B
Red phosphorus is obtained by heating "A" at 573 K, and can be converted to "B" by heating at 803 K under pressure.
A and B, respectively, are
$$\beta$$-black phosphorus and white phosphorus.
white phosphorus and $$\beta$$-black phosphorus.
$$\alpha$$-black phosphorus and white phosphorus.
white phosphorus and $$\alpha$$-black phosphorus.
Explanation
Red phosphrous is obtained by heating white phosphorous at $573 \mathrm{~K}$ in inert atmosphere. When red phosphorous is heated in a sealed tube at $803 \mathrm{~K}$, we get $\alpha$-black phosphorous.
$\beta$-Black phosphorous is prepared by heating white phosphorous at $473 \mathrm{~K}$ under high pressure.
$\beta$-Black phosphorous is prepared by heating white phosphorous at $473 \mathrm{~K}$ under high pressure.
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