What is the total number of donor atoms present in Tetracyanonickelate(II) ion?

Half life of a first order reaction is 900 minute at 400 K , find its half life at 300 K ?

$$ \left(\frac{\mathrm{E}_{\mathrm{a}}}{2.303 \mathrm{R}}=1.3056 \times 10^3\right) $$

Which solvent from following is used in order to avoid creation of waste and pollution of air?

For the cell,

${ }^{\ominus} \mathrm{Zn}_{(\mathrm{s})}\left|\mathrm{Zn}^{+2}(1 \mathrm{M})\right|\left|\mathrm{Ag}^{+1}(1 \mathrm{M})\right| \mathrm{Ag}_{(\mathrm{s})}{ }^{\oplus}$

If concentration of $\mathrm{Zn}^{+2}$ decreases to 0.1 M at 298 K , then emf of cell