Consider the gas phasereaction 2NO(g)+Cl2(g)-->2NOCL(g). Studies show that the i
ID: 683739 • Letter: C
Question
Consider the gas phasereaction 2NO(g)+Cl2(g)-->2NOCL(g). Studies show that the initialrate of disappearance of NO(g) is eight times faster when theconcentrations of both reactants are doubled and twice as fast whenthe concentration of chlorine alone is doubled. a) What is the order of this reaction with respect toCl2(g)? b) What is the order of theis reaction with respect toNO(g)? c) What is the rate law for this reaction? Consider the gas phasereaction 2NO(g)+Cl2(g)-->2NOCL(g). Studies show that the initialrate of disappearance of NO(g) is eight times faster when theconcentrations of both reactants are doubled and twice as fast whenthe concentration of chlorine alone is doubled. a) What is the order of this reaction with respect toCl2(g)? b) What is the order of theis reaction with respect toNO(g)? c) What is the rate law for this reaction?Explanation / Answer
The observation that the rate doubles when [ Cl2 ]doubles indicates that the rate is first order with respect toCl2. First order means "directly proportional to".
The observation that the rate increases 8-fold when [Cl2 ] and [ NO ] are doubled simultaneously indicatesthat the rate is second-order with respect to NO. Half of therate increase come from doubling [ Cl2 ], leaving 4-foldto come from doubling [ NO ] (i.e., 8-fold divided by 2-fold= 4-fold). Four-fold is 22.
Since rate “orders” reflect exponents in the ratelaw f = k [ A ]a [ B ]b .., herethe rate law equation is
r = k [ Cl2 ] [ NO ]2