MCQ
Impure phosphine is combustible due to presence of
- ✓$P_2H_4$
- B$N_2$
- C$PH_5$
- D$P_2O_5$
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$(I)$ They have high melting points, higher than those of pure metals
$(II)$ They are very hard
$(III)$ They retain metallic conductivity
$(IV)$ They are chemically more reactive than the pure metals

$(I)\,\,Zn\,+\,Conc. HNO_3\,(hot) \to Zn(NO_3)_2\,+\,X\,+\,H_2O$
$(II)\,\,Zn\,+\,dil. HNO_3\,(Cold) \to Zn(NO_3)_2\,+\,Y\,+\,H_2O$
Compound $X$ and $Y$ are respectively
