Identify the product obtained when phenol of heated with Zn dust.

For a zero order reaction $\mathrm{A} \longrightarrow$ product. Conc. of $A$ decreases from $0.8 \mathrm{~mol} \mathrm{~dm}^{-3}$ to $0.2 \mathrm{~mol} \mathrm{~dm}^{-3}$ in 6 minute. What is rate constant of the reaction?

Find value of Q from following equations.

(i) $\mathrm{C}_{(\mathrm{s})}+\mathrm{O}_{2(\mathrm{~g})} \longrightarrow \mathrm{CO}_{2(\mathrm{~g})} \Delta \mathrm{H}=\mathrm{QkJ}$

(ii) $\mathrm{C}_{(\mathrm{s})}+\frac{1}{2} \mathrm{O}_{2(8)} \longrightarrow \mathrm{CO}_{2(8)} \Delta \mathrm{H}=-\mathrm{x} \mathrm{kJ}$

(iii) $\mathrm{C}_{(\mathrm{s})}+\frac{1}{2} \mathrm{O}_{2(\mathrm{~s})} \longrightarrow \mathrm{CO}_{2(\mathrm{~g})} \Delta \mathrm{H}=-\mathrm{ykJ}$

"A given compound always contains the same proportion of elements" is a statement of -