For a reaction taking place in three steps at same temperature, overall rate constant $$\mathrm{K}=\frac{\mathrm{K}_1 \mathrm{~K}_2}{\mathrm{~K}_3}$$. If $$\mathrm{Ea}_1, \mathrm{Ea}_2$$ and $$\mathrm{Ea}_3$$ are 40, 50 and $$60 \mathrm{~kJ} / \mathrm{mol}$$ respectively, the overall $$\mathrm{Ea}$$ is ________ $$\mathrm{kJ} / \mathrm{mol}$$.

From the compounds given below, number of compounds which give positive Fehling's test is _________.

Benzaldehyde, Acetaldehyde, Acetone, Acetophenone, Methanal, 4nitrobenzaldehyde, cyclohexane carbaldehyde.

Number of compounds with one lone pair of electrons on central atom amongst following is _________.

$$\mathrm{O}_3, \mathrm{H}_2 \mathrm{O}, \mathrm{SF}_4, \mathrm{ClF}_3, \mathrm{NH}_3, \mathrm{BrF}_5, \mathrm{XeF}_4$$

Number of compounds among the following which contain sulphur as heteroatom is ___________.

Furan, Thiophene, Pyridine, Pyrrole, Cysteine, Tyrosine