Why is K unitless?

[Ellis Song 4I]

Why does the equilibrium constant, K, not have units?

[Abhi Vempati 2H]

We use reactivity to calculate K, and concentrations/partial pressures are just an approximation of the reactivities. Reactivities have no units, so K will therefore not have any units. This was covered in the modules and lectures in further detail. Hope this helps!

[KnarGeghamyan1B]

When we set up the equation for K, it is K= [M]/[M], as in a concentration over another concentration. So just think of it as canceling out the units M in the fraction, leaving you with a unitless number.

[Tai Metzger 3K]

K is essentially a ratio (between products and reactants) and so it does not have units.

[annikaying]

K is a ratio and therefore is moreso a comparison than a value. You can also think of the units as canceling as the units on top equal that of the bottom.

[Jocelyn Thorp 1A]

it's just a constant representing the ratio of the concentrations. Looking at the units, they would cancel each other out :)

[Diana Andrade_4F]

K is just a ratio of products/reactants, so there are no units. Also, when calculating K, the units just cancel out.

[Megan Kirschner]

K is y a ratio (between products and reactants) and so it does not have units- but so does this mean that all ratios we use in this class will be unitless? Is it safe to apply this rule widely?

[Jocelyn Thorp 1A]

K is y a ratio (between products and reactants) and so it does not have units- but so does this mean that all ratios we use in this class will be unitless? Is it safe to apply this rule widely?

If it's simply a ratio then most likely, yes. Constants will come with their units but ratios should remain unitless.

[Timmy Nguyen Dis 1I]

K is simply a ratio between molarities, so that's why it has no units.

[Sreyes_1C]

because its concentrations over concentrations, the M cancels out and its also just a ratio of the concentrations