Which from following polymers is biodegradable?

The standard emf for cell, ${ }^{\ominus} \mathrm{Cd}_{(\mathrm{s})}\left|{ }^{+2} \mathrm{Cd}(1 \mathrm{M}) \| \stackrel{+2}{\mathrm{Cu}}(1 \mathrm{M})\right| \mathrm{Cu}_{(\mathrm{s})}{ }^{\oplus}$ is 0.74 V .

If concentration of $\mathrm{Cd}_{(\mathrm{aq})}^{+2}$ and $\mathrm{Cu}_{(\mathrm{aq})}^{+2}$ decreases by 10 times at 298 K . Calculate emf of cell.

Calculate the equilibrium concentration of $\mathrm{Pb}^{++}$ions in a solution of PbS containing $1 \times 10^{-11} \mathrm{~mol} \mathrm{dm}^{-3}$ of sulphide ions.

(Given $\mathrm{K}_{\mathrm{sp}}$ for $\mathrm{PbS}=8.0 \times 10^{-28}$ )

A first order reaction is $50 \%$ completed in 16 minutes. Find the percentage of reactant reacting in 32 minutes.