Question

what is the concentration of ammonium chloride in a solution of ph 4.80?​

Answer 1

Answer:You can see from the pH that the ammonium chloride solution is acidic. This is due the presence of the ammonium ion which is the conjugate acid of ammonia, a weak base.

In water, the following equilibrium is established:

NH4+(aq) + H2O(l) = NH3(aq) + H3O+(aq)

The Ka for this system can be determined from the Kb of ammonia: Ka = Kw/Kb

So, Ka = 1.0x10^-14/1.8x10^-5 = 5.6x10^-10

The concentration of the NH4Cl solution will equal the concentration of the (NH4+)aq.

If we allow the initial concentration of NH4+ be represented by “y” and the change in concentrations that occur as the system reaches equilibrium be represented by “x”, then the equilibrium concentrations of the components can be expressed as follows:

[NH4+] = (y-x) [NH3] = x and [H3O+] = x

To simplify things, since the Ka for this system is very small we can assume that for the [NH4+] = (y-x) = y as the value of “x” will be very small.

Now because we know the pH of the system we can calculate the [H3O+] which will give us the value of “x”.

[H3O+] = 10^-pH = 1.58x10^-5 M = x

We can now substitute these values into the Ka equation and solve for “y”:

5.6x10^-10 = [NH3][H3O+]/[NH4+]

5.6x10^-10 = (x)(x)/y

5.6x10^-10 = (1.58x10^-5)^2/y

y =(1.58x10^-5)^2/5.6x10^-10 = 0.45M

So, the concentration of NH4Cl is 0.45 M

Explanation:

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