Calculate the molar concentration of OH ions in a 0.066 M solution of ethylamine (C2H5NH2: Kb= 6.4 x 10-) Express your answer to two significant figures.

6.5x10⁻³M = [OH⁻]

Explanation:

The Kb of a Weak base as ethylamine is expressed as follows:

Kb = [OH⁻] [C₂H₅NH₃⁺] / [C₂H₅NH₂]

As the equilibrium of ethylenamine is:

C₂H₅NH₂(aq) + H₂O(l) ⇄ C₂H₅NH₃⁺(aq) + OH(aq)

The concentration of C₂H₅NH₃⁺(aq) + OH(aq) is the same because both ions comes from the same equilibrium. Thus, we can write:

Kb = [OH⁻] [C₂H₅NH₃⁺] / [C₂H₅NH₂]

6.4x10⁻⁴ = [X] [X] / [C₂H₅NH₂]

Also, we can assume the concentration of ethylamine doesn't decrease. Replacing:

6.4x10⁻⁴ = [X] [X] / [0.066M]

4.224x10⁻⁵ = X²

6.5x10⁻³M = X

the best answer is d because the strong cohesion is caused by the ability of water molecules to undergo hydrogen bonding.

a is incorrect because when water solidifies, it becomes   ice, which expands and occupies a bigger volume for the same mass of water in its liquid state.

b is incorrect because water has high surface tension. besides bonding to itself it hydrogen bonds to other molecules at the top decreasing possibility for breaking of attractive forces.

c is incorrect because the water molecule has oxygen which is highly electronegative and so pulls the electron pair towards itself creating a dipole moment, making the molecule polar.

e is incorrect because water has strong adhesion, ability to stick to other molecules such as glass because of this molecules having stronger hydrogen bonding than water.

50.23 i believe is correct but don't quote me on that.