# Why is N_2O_5 not widely used as a laboratory reagent? On the other hand, why is P_2O_5, and CaO, and H_2SO_4 widely used?

Because we could not put ${N}_{2} {O}_{5}$ into a bottle........
${P}_{4} {O}_{10}$, and $C a O$ are both solids that we could conveniently deploy with a spoon. ${H}_{2} S {O}_{4}$, as a liquid, is a little bit less convenient.
But ${N}_{2} {O}_{5}$ is not something you could put in a bottle; it is also pretty unstable stuff, and would be used with caution..........