Q17.8P - Chemistry: Molecular Nature Of Matter And Change

Question

In a study of formation of HI from its elements, 
${\mathbf{H}}_{\mathbf{2}}\mathbf{\left(}\mathbf{g}\mathbf{\right)}\mathbf{+}{\mathbf{I}}_{\mathbf{2}}\mathbf{\left(}\mathbf{g}\mathbf{\right)}\mathbf{\rightleftharpoons }\mathbf{2}\mathbf{HI}\mathbf{\left(}\mathbf{g}\mathbf{\right)}$

Equal amounts of hydrogen and iodine were placed in a container which was then sealed and heated.

(a) On one set of axes, sketch concentration vs. Time curves for hydrogen and hydrogen iodide, and explain how Q changes as a function of time.

(b) Is the value of Q different if [iodine] is plotted instead of [hydrogen]?

Step-by-Step Solution

Answer

(a) 

(b) No

Step 1: Reaction Quotient

The reaction quotient is the ratio of concentration of products to the reactants raised to their coefficient powers. This gives the relative amount of substances present in a chemical reaction. It is represented by the letter ‘Q’.

Step 2: Subpart (a)

The graph is as shown below.

The concentration of reactant decreases with time and the concentration of product increases with time. 

The reaction quotient Q increases with respect to the increase in concentration of product and decrease with increase in concentration of reactants with time.

Step 2: Subpart (b)

The given reaction for the formation of HI shows that one mole of hydrogen react with one mole of iodine to give  . The concentration of hydrogen and iodine varies in a similar way.

Hence, on plotting the graph with concentration of iodine instead of concentration of hydrogen vs. time, we get the same plot.