## units

$aR \to bP, Rate = -\frac{1}{a} \frac{d[R]}{dt} = \frac{1}{b}\frac{d[P]}{dt}$

Rhea Shah 2F
Posts: 97
Joined: Thu Jul 25, 2019 12:17 am

### units

How do I determine the units of k for a reaction?

SnehinRajkumar1L
Posts: 101
Joined: Thu Jul 11, 2019 12:15 am

### Re: units

In your rate law equation, you'd multiply out the units of the reactants to find the units.

JonathanS 1H
Posts: 101
Joined: Thu Jul 11, 2019 12:17 am

### Re: units

The equilibrium constant, K has no units. If you mean rate constant, k, then the units are mol.L-1.s-1 for a zero order reaction, s-1 for a first order reaction, and L.mol-1.s-1 for a second order reaction.

Cavalli_1H
Posts: 92
Joined: Thu Sep 19, 2019 12:15 am

### Re: units

K is a relative ratio so from my understanding it has no specific units

KHowe_1D
Posts: 103
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Been upvoted: 1 time

### Re: units

K (the equilibrium constant) has no units.

VLi_2B
Posts: 99
Joined: Sat Sep 14, 2019 12:15 am

### Re: units

K = equilibrium constant has no units
k = rate constant units fluctuate between orders

0 order units: M/s, M/min, M/hr, etc.
1st order units: s-1, min-1, hr-1, etc.
2nd order units: M-1s-1, M-1min-1, M-1hr-1, etc.

Chris Charton 1B
Posts: 69
Joined: Mon Jun 17, 2019 7:23 am

### Re: units

The equilibrium constant does not have units

chari_maya 3B
Posts: 108
Joined: Sat Sep 07, 2019 12:18 am

### Re: units

There is a chart explaining this on page 595 of the textbook

Areli C 1L
Posts: 95
Joined: Wed Nov 14, 2018 12:19 am

### Re: units

I don't think K has units? thought it was unitless since its an EQ constant.

Niharika 1H
Posts: 50
Joined: Thu Jul 25, 2019 12:16 am

### Re: units

the rate constant k has units s-1 for a first order reaction, and (L*mol-1*s-1) for a second order reaction.

Nathan Rothschild_2D
Posts: 131
Joined: Fri Aug 02, 2019 12:15 am

### Re: units

for 0 order reactions the units are M/s (or any unit for time)

Zoya Mulji 1K
Posts: 105
Joined: Thu Jul 11, 2019 12:15 am

### Re: units

the units will depend on the rate law and the order of the reaction because that will influence the power to which the units are multiplied. I would find the answer and then write out the formula with just the units to calculate/find what those would be.

Orrin Zhong 4G
Posts: 51
Joined: Sat Jul 20, 2019 12:16 am

### Re: units

k has different units depending on what order the reaction is. Since rate has units (mol x L)/s, you just set up a unit equation: mol x L/s = k x (mol x L)^(order of rxn) and solve for the units of k.