If the acid dissociation constant, Ka, for an acid HA is 8 x 104 at 25°C, what percent of the acid is dissociated in a 0.50 M solution of HA at 25°C?

A

08%

Percent dissociated = 3.92%

Explanation:

The equilibrium of the weak acid, HA, is:

HA ⇄ H⁺ + A⁻

Where Ka = 8x10⁻⁴ is: [H⁺] [A⁻] / [HA]

As both H⁺ and A⁻ comes from the same equilibrium we can write the concentrations of the species as follows:

[H⁺] = X

[A⁻] = X

[HA] = 0.50M - X

Where X is reaction coordinate

Replacing:

8x10⁻⁴ = X² / 0.50-X

4x10⁻⁴ - 8x10⁻⁴X - X² = 0

Solving for X:

X = -0.02M. False solution. There is no negative concentrations

X = 0.0196M. Right solution.

Replacing:

[A⁻] = 0.0196M

Percent of the acid that is dissociated is:

[A⁻] / [HA]₀ * 100

[HA]₀ is its initial concentration = 0.50M

0.0196M / 0.50M * 100

in chemistry, adhesion and cohesion are attractive forces that exist between molecules. they hold the molecules together from each other. they are different in that adhesive force exists between molecules of different substance while cohesive force happens between molecules of same substance.

adhesion between water and glass causes water molecules at the edge of water and glass interface to climb up the wall in a narrow glass tube. this is called capillary action. cohesion is what gives glass its shape and causes water to form a droplet.