MCQ
The oxide that shows magnetic property is :
- A$SiO _{2}$
- ✓$Mn _{3} O _{4}$
- C$Na _{2} O$
- D$MgO$
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$N{H_4}^ + + {S^{ - 2}} \rightleftharpoons N{H_3} + H{S^ - }$

$\frac{1}{2}{P_4}(s) + 3C{l_2}(g) \to 2PC{l_3}(l)\,;$ $\Delta H=-635 \,kJ$
$PC{l_3}(l) + C{l_2}(g) \to PC{l_5}(s)\,;$ $\Delta H=-137\, kJ$
The value of heat of formation of $PCl_5$ is ......$kJ\,mol^{-1}$