Which one of the following reactions is NOT possible?

The number of ions from the following that have the ability to liberate hydrogen from a dilute acid is _________.

$$\mathrm{Ti}^{2+}, \mathrm{Cr}^{2+} \text { and } \mathrm{V}^{2+}$$

The number of moles of methane required to produce $$11 \mathrm{~g} \mathrm{~CO}_2(\mathrm{g})$$ after complete combustion is : (Given molar mass of methane in $$\mathrm{g} \mathrm{~mol}^{-1}: 16$$ )

The quantity of silver deposited when one coulomb charge is passed through $$\mathrm{AgNO}_3$$ solution :