Rate of a reaction decreases with the passage of time as the concentration of reactants decrease. Conversely, rates generally increase when reactant concentrations increase. So, rate of a reaction depends upon the concentration of reactants.
Consider a general reaction
aA + bB → cC + dD
where a, b, c and d are the stoichiometric coefficients of reactants and products.
The rate expression for this reaction is
Rate ∝ [A]x [B]y
where exponents x and y may or may not be equal to the stoichiometric coefficients (a and b) of the reactants.
Above equation can also be written as Rate = k [A]x [B]y
-\(\frac{dR}{dT}\) = k [A]x [B]y
This form of equation is known as differential rate equation, where k is a proportionality constant called rate constant.
The rate of the elementary reaction 2NO + O2 → 2NO2 when the volume of the reaction vessel is halved, what is the change in the rate of reaction?
Answer & explanation
Correct answer: option 1
For the elementary reaction 2NO + O2 → 2NO2
r = k [NO]2[O2]1
If volume of the vessel is halved, concentration of each reactant becomes doubled.
r' = k[2NO]2[2O2]1
r' = 8r