The reaction $2\mathrm{NO}\left(\mathrm{g}\right)+{\mathrm{Cl}}_2\left(\mathrm{g}\right)\to 2\mathrm{NOCl}\left(\mathrm{g}\right)$ is carried out in a sealed tube. At the start of the experiment, the concentration of both $\mathrm{NO}$ and $\mathrm{Cl}$, was $0.01 \mathrm{mol} {\mathrm{dm}}^{-3}$ The reaction is second order with respect to $\mathrm{NO}$ and first order with respect to $\mathrm{Cl}$. Which one of these represents the rate of reaction when the concentration of $\mathrm{NO}$ falls to $0.005 \mathrm{mol} {\mathrm{dm}}^{-3}$?

State whether the below given pair of substances might catalyse the reaction: ${\mathrm{S}}_2{{\mathrm{O}}_8}^{2–} \left(\mathrm{aq}\right) + 2{\mathrm{I}}^{–} \left(\mathrm{aq}\right) \to 2{{\mathrm{SO}}_4}^{2–} \left(\mathrm{aq}\right) + {\mathrm{I}}_2\left(\mathrm{aq}\right)$

${\mathrm{Ni}}^{2+}\left(\mathrm{aq}\right) / \mathrm{Ni}\left(\mathrm{s}\right) {\mathrm{E}}^{⊝}= –0.25 \mathrm{V}$

Explain your answer.

Given : ${\mathrm{E}}^{⊝}$ of ${\mathrm{S}}_2{{\mathrm{O}}_8}^{2-} /{{\mathrm{SO}}_4}^{2-}$is $+2.01 \mathrm{V}$ and  ${\mathrm{E}}^{⊝}$ of ${\mathrm{I}}^{-} /{\mathrm{I}}_2$ is $+0.54 \mathrm{V}$. 

State whether the below given pair of substances might catalyse the reaction: ${\mathrm{S}}_2{{\mathrm{O}}_8}^{2–} \left(\mathrm{aq}\right) + 2{\mathrm{I}}^{–} \left(\mathrm{aq}\right) \to 2{{\mathrm{SO}}_4}^{2–} \left(\mathrm{aq}\right) + {\mathrm{I}}_2\left(\mathrm{aq}\right)$

${\mathrm{Mn}}^{3+}\left(\mathrm{aq}\right) / {\mathrm{Mn}}^{2+}\left(\mathrm{aq}\right) {\mathrm{E}}^{⊝}= +1.49 \mathrm{V}$

Explain your answer.

Given : ${\mathrm{E}}^{⊝}$ of ${\mathrm{S}}_2{{\mathrm{O}}_8}^{2-} /{{\mathrm{SO}}_4}^{2-}$is $+2.01 \mathrm{V}$ and  ${\mathrm{E}}^{⊝}$ of ${\mathrm{I}}^{-} /{\mathrm{I}}_2$ is $+0.54 \mathrm{V}$. 

State whether the below given pair of substances might catalyse the reaction: ${\mathrm{S}}_2{{\mathrm{O}}_8}^{2–} \left(\mathrm{aq}\right) + 2{\mathrm{I}}^{–} \left(\mathrm{aq}\right) \to 2{{\mathrm{SO}}_4}^{2–} \left(\mathrm{aq}\right) + {\mathrm{I}}_2\left(\mathrm{aq}\right)$

${\mathrm{Ce}}^{4+}\left(\mathrm{aq}\right)/{\mathrm{Ce}}^{3+}\left(\mathrm{aq}\right) {\mathrm{E}}^{⊝}= +1.70 \mathrm{V}$

Explain your answer.

Given : ${\mathrm{E}}^{⊝}$ of ${\mathrm{S}}_2{{\mathrm{O}}_8}^{2-} /{{\mathrm{SO}}_4}^{2-}$is $+2.01 \mathrm{V}$ and  ${\mathrm{E}}^{⊝}$ of ${\mathrm{I}}^{-} /{\mathrm{I}}_2$ is $+0.54 \mathrm{V}$. 

State whether the below given pair of substances might catalyse the reaction: ${\mathrm{S}}_2{{\mathrm{O}}_8}^{2–} \left(\mathrm{aq}\right) + 2{\mathrm{I}}^{–} \left(\mathrm{aq}\right) \to 2{{\mathrm{SO}}_4}^{2–} \left(\mathrm{aq}\right) + {\mathrm{I}}_2\left(\mathrm{aq}\right)$

${\mathrm{Cu}}^{2+}\left(\mathrm{aq}\right)/{\mathrm{Cu}}^{+}\left(\mathrm{aq}\right) {\mathrm{E}}^{⊝}= +0.15 \mathrm{V}$

Explain your answer.

Given : ${\mathrm{E}}^{⊝}$ of ${\mathrm{S}}_2{{\mathrm{O}}_8}^{2-} /{{\mathrm{SO}}_4}^{2-}$is $+2.01 \mathrm{V}$ and  ${\mathrm{E}}^{⊝}$ of ${\mathrm{I}}^{-} /{\mathrm{I}}_2$ is $+0.54 \mathrm{V}$. 

Describe in terms of oxidation number change, which species are being oxidised and which are being reduced in following equation:

${\mathrm{SO}}_2\left(\mathrm{g}\right) + {\mathrm{NO}}_2\left(\mathrm{g}\right) \to {\mathrm{SO}}_3\left(\mathrm{g}\right) + \mathrm{NO}\left(\mathrm{g}\right)$

Describe in terms of oxidation number change, which species are being oxidised and which are being reduced in following equation:

$\mathrm{NO} + \frac{1}{2}{\mathrm{O}}_2 \to {\mathrm{NO}}_2$

Nickel acts as a catalyst for the hydrogenation of alkenes. For example: ${\mathrm{CH}}_2={\mathrm{CH}}_2 + {\mathrm{H}}_2 \stackrel{\mathrm{Ni} }{\to }{\mathrm{CH}}_3-{\mathrm{CH}}_3$

Suggest how nickel catalyses this reaction by referring to the processes of adsorption, reaction on the metal surface and desorption.