Calculate the hydroxide concentration of a solution that is 0.1 F with NH3, and
0.25 F in respect to (NH4)2S04.
To calculate the hydroxide (OH-) concentration of a solution, we need to consider the dissociation of the provided compounds.
First, let's focus on the compound NH3 (ammonia). Ammonia is a weak base that undergoes partial dissociation in water.
The dissociation equation for NH3 is as follows:
NH3 + H2O ⇌ NH4+ + OH-
The F (Formal) concentration of NH3 corresponds to the concentration of NH4+ ions formed in the solution. Since NH3 is a weak base, we can assume that NH4+ concentration is equal to the NH3 concentration.
Given that the NH3 concentration is 0.1 F, we can assume that the NH4+ and OH- concentrations are also 0.1 F.
Now let's consider the compound (NH4)2SO4 (ammonium sulfate).
(NH4)2SO4 dissociates completely in water into two ammonium ions (NH4+) and one sulfate ion (SO4^2-).
So, the F concentration of (NH4)2SO4 directly reflects the concentration of NH4+ ions in the solution. Therefore, the NH4+ concentration is 0.25 F.
Since the NH4+ concentration is known, we can assume the OH- concentration to be equal to zero because (NH4)2SO4 does not directly provide OH- ions.
Therefore, the hydroxide concentration in this solution is 0 F.
To calculate the hydroxide concentration of a solution, we need to use the dissociation constant (Kb) for NH3, which is the base involved in this solution. The Kb for NH3 is 1.8 x 10^-5 at 25°C.
First, we need to determine the concentration of NH3. In this case, the concentration is given as 0.1 F.
Next, we'll use the Kb value and the concentration of NH3 to calculate the hydroxide concentration. The hydroxide concentration can be determined using the following equation:
Kb = [OH-][NH3]/[NH4+]
Given the concentration of NH3 (0.1 F), let's assume the hydroxide concentration is x M. Since NH3 is a weak base, we can consider the concentration of NH4+ to be negligible compared to [NH3].
Now, substitute the values into the equation:
Kb = x * 0.1 F / [NH4+]
1.8 x 10^-5 = x * 0.1 F / [NH4+]
To solve for x, we need to determine the concentration of NH4+. We're given that the solution is 0.25 F with respect to (NH4)2SO4, so we can assume that the concentration of NH4+ will be 0.25 F.
Plug in the values:
1.8 x 10^-5 = x * 0.1 F / 0.25 F
To isolate x, we can multiply both sides of the equation by 0.25 F:
1.8 x 10^-5 * 0.25 F = x * 0.1 F
4.5 x 10^-6 F = 0.1 x
Now, divide both sides of the equation by 0.1 F:
4.5 x 10^-6 F / 0.1 F = x
4.5 x 10^-5 M = x
Therefore, the hydroxide concentration of the solution is 4.5 x 10^-5 M.
NH3 + H2O ==> NH4^+ + OH^-
and
(NH4)2SO4 ==> 2NH4^+ + SO4^2-
If [(NH4)2SO4] = 0.25 then [(NH4)^+] = 0.50
Use Kb = (NH4^+)(OH^-)/(NH3).
You know Kb, (NH4)^+ and (NH3). Solve for OH^-
You could use the Henderson-Hasselbalch equation, too, if you've had that in your course.