For a solution that is 0.168 M NH3 and 0.104 M NH4Cl calculate the following.?
[OH-]
[NH4+]
[Cl-]
[H3O+]
How would you do this :-/
NH4Cl is a salt. Therefore, when dissolve it will give you (NH4^+) = 0.104M and Cl^- will be 0.104M.
Determine pH from the Henderson-Hasselbalch equation, then find H^+ from that and OH^- from (H^+)(OH^-) = Kw = 1E-14
But for that wouldn't you need to know the pKa?
nvm got it!
Yes. pKa for NH3 = Kw/Kb
To calculate the concentrations of different ions in a solution, you need to understand the concept of dissociation and the ionization equations for the given compounds.
NH3 is a weak base, and it undergoes partial ionization in water according to the following equation:
NH3 + H2O ⇌ NH4+ + OH-
NH4Cl is a salt that dissociates completely in water, giving NH4+ and Cl- ions.
Let's start with calculating [OH-].
1. Calculate the concentration of OH- ions:
Since NH3 undergoes partial ionization, we need to find the concentration of OH- ions from the concentration of NH3 using the ionization equation.
The initial concentration of NH3 is 0.168 M, but only a fraction of it ionizes. Let's assume 'x' is the fraction of NH3 that ionizes. Then, the concentration of NH4+ ions will also be 'x' M, and the concentration of OH- ions will also be 'x' M.
NH3 + H2O ⇌ NH4+ + OH-
From the stoichiometry of the ionization equation, we can see that for every 1 mole of NH3 that ionizes, 1 mole of OH- ions is produced. So, the concentration of OH- ions will be equal to 'x'.
To calculate 'x', we need to use the dissociation constant for NH3, which is the equilibrium constant for the ionization reaction. The dissociation constant (Kw) for NH3 is usually given as 1.8 × 10^-5. However, if the value is not provided, you can calculate it using the value of the base dissociation constant (Kb) for NH3.
Kw = [NH4+][OH-] / [NH3]
Using the given concentration of NH3 (0.168 M), we have:
1.8 × 10^-5 = (x)(x) / (0.168 - x)
This is a quadratic equation, and solving it will give you the value of 'x', which is the concentration of OH- ions.
2. Calculate the concentration of NH4+ ions:
Since NH4Cl is a salt that dissociates completely, the concentration of NH4+ ions will be equal to the initial concentration of NH4Cl, which is 0.104 M.
3. Calculate the concentration of Cl- ions:
Since NH4Cl is a salt that dissociates completely, the concentration of Cl- ions will also be equal to the initial concentration of NH4Cl, which is 0.104 M.
4. Calculate the concentration of H3O+ ions:
Since NH3 is a weak base and produces OH- ions, the concentration of H3O+ ions can be obtained using the fact that the product of [H3O+] and [OH-] in water is a constant (1.0 × 10^-14 at 25°C).
[H3O+][OH-] = 1.0 × 10^-14
Substitute the value of [OH-] (which we calculated in step 1) into this equation and solve for [H3O+] to get the concentration of H3O+ ions.
It is important to note that the values obtained above are approximate, assuming that the solution is ideal and concentration changes are negligible.