Zeroeth, First, Second meaning

[Siddiq 1E]

Hi, I was working on HW question 7A.7 and it made me realize I don't really understand what it means if a reaction is first order? I know how to tell based on the graph etc, but what does it mean in terms of units and reaction speed etc?

[Chem_Mod]

First order just means that the reaction rate is dependent on the concentration of only one reactant in a 1 to 1 relationship.

rate = k [A]¹

[Paul Hage 2G]

Also, for a first-order reaction, ln[A]=-kt+ln[A]₀

[Leonardo Le Merle 1D]

Also, note that just because a reactant is first order, doesn't necessarily mean the reaction itself is as well. If multiple reactants are first order, the reaction is the sum of those reactants (So if N and O were both first order in forming NO, the reaction is second order).

[Tanmay Singhal 1H]

first order means that rate of reaction is proportional to concentration of reacting substance

[Myka G 1l]

In a first order reaction, the rate of reaction is directly proportional to the concentration of a single reacting substance. Whereas in a 2nd order reaction the rate depends on the concentration of 2 reacting first order substances or a single reactant with a squared concentration. Because it depends on a single substance, the graph of a first order reaction is a straight line. For a zeroth order reaction the rate is solely dependent on the rate constant.

[Shutong Hou_1F]

The units of k:
first-order: s^-1, second-order: (s^-1)*(mol^-1)*(L), zero-order: (mol)(L^-1)*(s^-1);