Question

The unit of rate constant for the zero-order reaction is:
A.)${ s }^{ -1 }$
B.)${ molL }^{ -1 }{ s }^{ -1 }$
C.)${ Lmol }^{ -1 }{ s }^{ -1 }$
D.)${ { L }^{ 2 }mol }^{ -2 }{ s }^{ -1 }$

Answer 1

The zero-order reaction can be defined as the rate of the reaction is proportional to the zero power of the concentration of reactants [R]. This means the rate is independent of the concentration of the reactant.

Complete answer:
For a zero-order reaction:
${ Rate= }\frac { dC }{ dt } { =k\left[ { R }_{ 0 } \right] ^{ \circ } }$
${ k= }\frac { dC }{ dt } { = }\frac { concentration }{ time }$
${ k= }\frac { mol{ L }^{ -1 } }{ s }$
k =${ molL^{ -1 }{ s }^{ -1 }}$

So, the correct answer is “Option B”.

Additional Information:
a.)The rate constant is equal to the rate of reaction when the concentration of all the reactants is taken as unity.
b.)The rate constant is nearly doubled with a rise in temperature by ${ 10 }^{ \circ }$ for a chemical reaction.
c.)Few examples of zero-order reaction are:

The photochemical reaction between hydrogen and chlorine
Decomposition of ${ N }_{ 2 }{ O }$ on a hot platinum surface.
The decomposition of ${ NH }_{ 3 }$ in the presence of molybdenum or tungsten is a zero-order reaction.
Iodination of acetone in the presence of ${ H }^{ + }$ ions.

d.)Zero-order reactions generally occur under the heterogeneous system. In such a system, the reactant is adsorbed on the surface of a solid catalyst, where it is converted into a product. The fraction of the surface of the catalyst covered by the reactant is proportional to the concentration of a reactant at low values. However, after a certain concentration limit of the reactant, the reaction rate does not change i.e. rate becomes independent of concentration and the reaction becomes zero order.

Note:
The possibility to make a mistake just a little portion of the reactant particles are in an area or state wherein they can respond, and this division is consistently recharged from the bigger pool.