Unit cell of an element has edge length of 5$$\mathop A\limits^o $$ with density $4 \mathrm{~g} \mathrm{~cm}^{-3}$, if its atomic mass is 149, identify the crystal structure.

Which among the following gases is difficult to liquify?

Phenol on heating with zinc dust forms

The degree of dissociation of 0.01 M solution of $\mathrm{NH}_4 \mathrm{OH}$ is $4.2 \times 10^{-2}$. What is the percent dissociation of $\mathrm{NH}_4 \mathrm{OH}$ ?