Units Of Rate Constant MDCAT Quiz: Understand, because they are very essential in the interpretation and solution of problems concerning reaction rates. The units of the rate constant, k, are different for each reaction order. One needs to know how to deduce these units so that he or she may determine the rate law and compute the rate of reaction in any chemical process. MDCAT Quiz questions frequently test students’ ability to calculate and identify the correct units for the rate constant based on the order of the reaction.
Units of Rate Constant for Different Orders of Reaction
The units of the rate constant are directly related to the overall order of the reaction. For the general rate law expression: rate = k[A]^m[B]^n, where m and n are the orders of the reaction with respect to each reactant, the units of the rate constant depend on the sum of the exponents (the overall reaction order).
For a zero-order reaction, the rate law is rate = k, and the units of k are M/s (molarity per second).
For a first-order reaction, the rate law is rate = k[A], and the units of k are s⁻¹ (inverse seconds).
For a second-order reaction, the rate law is rate = k[A]^2 or rate = k[A][B], and the units of k are M⁻¹s⁻¹ (molarity inverse seconds).
Knowing these unit relationships is critical to answering many MDCAT Quiz questions that involve varying reaction orders and ask you to determine the appropriate units for the rate constant.
Importance of Units in Rate Constant Calculations
Correctly determining the units of the rate constant is important not only for the solution of the problem involving reaction rates but also for making the calculations dimensionally consistent. For MDCAT students, the ability to derive the correct units for the rate constant will help improve problem-solving accuracy. Free Flashcard tools can be an effective way to memorize the units for different reaction orders and practice applying them to various problems.
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Mastering the units of the rate constant is crucial to MDCAT success, especially in questions related to reaction kinetics. Through the use of MDCAT Quiz and Free Flashcard resources, students are able to reinforce their understanding of rate laws, rate constants, and units of the rate constants, ultimately improving their performance on the exam.
What is the unit of rate constant for a zero-order reaction?
mol L⁻¹ s⁻¹
What is the unit of rate constant for a first-order reaction?
s⁻¹
What is the unit of rate constant for a second-order reaction?
L mol⁻¹ s⁻¹
What is the unit of rate constant for a third-order reaction?
L² mol⁻² s⁻¹
What is the unit of rate constant for a reaction with order 1.5?
L⁰.⁵ mol⁻⁰.⁵ s⁻¹
For a fourth-order reaction, what is the unit of the rate constant?
L³ mol⁻³ s⁻¹
For a half-order reaction, what is the unit of the rate constant?
L⁰.⁵ mol⁻⁰.⁵ s⁻¹
For a zero-order reaction, what does the unit of k indicate?
molarity/time
For a first-order reaction, k is expressed in terms of __________.
time⁻¹
In a second-order reaction, k involves the product of __________ and time⁻¹.
concentration⁻¹
What is the derived unit of k for a second-order reaction in SI units?
m³ mol⁻¹ s⁻¹
For a zero-order reaction, k is directly proportional to __________.
concentration
In a third-order reaction, k is expressed in __________ units.
L² mol⁻² s⁻¹
For a first-order gas-phase reaction, the unit of k may also be expressed as __________.
atm s⁻¹
For a reaction of mixed order (2/3), k is expressed in __________.
L⁰.³ mol⁻⁰.³ s⁻¹
The unit of k for a pseudo-first-order reaction is equivalent to __________.
s⁻¹
For a zero-order reaction, the rate is independent of __________.
concentration
For a reaction with fractional order (1/2), the unit of k involves __________.
concentration⁻⁰.⁵
For a zero-order reaction, the unit of k is determined by dividing rate by __________.
concentration
For a reaction of negative order, the unit of k involves a positive exponent of __________.
concentration
For a second-order reaction, the unit of k is expressed as the inverse of __________.
concentration × time
For a first-order radioactive decay reaction, k is often expressed in __________.
s⁻¹
For a reaction with a large k value, the reaction is __________.
fast
For a zero-order photochemical reaction, k may involve units of __________.
mol m⁻² s⁻¹
For a reaction involving gases, the unit of k is often expressed in terms of __________.
pressure
For a bimolecular gas-phase reaction, the unit of k involves __________.
pressure⁻¹ time⁻¹
For a second-order reaction, k is proportional to the square of __________.
concentration
For a fourth-order reaction, k involves the cube of __________ in its unit.
concentration
For a reaction with fractional order (3/2), k is expressed in __________.
L⁰.⁵ mol⁻⁰.⁵ s⁻¹
For a pseudo-zero-order reaction, k is proportional to __________.
rate
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