For a zero order reaction will the molecularity be equal to zero? Explain.
No, the molecularity can never be zero or a fractional number as it shows the number of reactants taking part in a reaction which can never be zero.
For a general reaction $A \rightarrow B$, plot of concentration of $A$ vs time is given in figure. Answer the following questions on the basis of this graph.
(i) What is the order of the reaction?
(ii) What is the slope of the curve?
(iii) What are the units of rate constant?
(i) For $A \longrightarrow B$ the given graph shows a zero order reaction. Mathematically represented as
$$[R]=-k t+[R]_0$$
Which is equation of straight line. Hence, reaction is a zero order.
(ii) Slope $=-k$
(iii) Unit of zero order reaction is $\mathrm{mole~L}^{-1} \mathrm{~s}^{-1}$.
The reaction between $\mathrm{H}_2(g)$ and $\mathrm{O}_2(g)$ is highly feasible yet allowing the gases to stand at room temperature in the same vessel does not lead to the formation of water. Explain.
Because activation energy of the reaction is very high at room temperature but at high temperature H - Hand O - O bond break and colliding particles cross the energy barrier. This is why reaction between $\mathrm{H}_2(\mathrm{~g})$ and $\mathrm{O}_2(\mathrm{~g})$ does not lead to formation of water at room temperature while keeping in the same vessel.
Why does the rate of a reaction increase with rise in temperature?
At higher temperatures, larger fraction of colliding particles can cross the energy barrier (i.e., the activation energy) which leads to faster rate.
Oxygen is available in plenty in air yet fuels do not burn by themselves at room temperature. Explain.
For combustion reactions, activation energy of fuels is very high at room temperature. So, fuels do not burn by themselves at room temperature.