Determine the hydroxide ion concentration in a solution that is 0.0004 M HCl.

Answer in units of M.
I have no idea how to start, I just need to know what I need to solve for and to set it up, I know the formula pOH^-=-log[OH^-] I just don't know where to plug things in and solve

HCl is a strong acid so, determine the pH:

pH=-log[HCl]

pH+pOH=14

14-pH=pOH

Since pOH=-log[OH^-]

10^-(pOH)=[OH]

To determine the hydroxide ion concentration in a solution, you can use the concept of the auto-ionization of water. In pure water, the concentration of hydrogen ions (H+) is equal to the concentration of hydroxide ions (OH-), which can be expressed as:

[H+] = [OH-] = 1 x 10^-7 M

However, in the presence of a strong acid like HCl, the concentration of H+ ions will be significantly higher than 1 x 10^-7 M, causing a decrease in [OH-].

Since HCl completely ionizes in solution, the concentration of H+ ions will be equal to the concentration of HCl. In this case, the concentration of HCl is 0.0004 M.

So, we need to first find the concentration of H+ ions and then use it to determine the concentration of OH- ions.

[H+] = 0.0004 M

Since [H+] = [OH-], the concentration of OH- ions is also 0.0004 M.

Therefore, the hydroxide ion concentration in the given solution is 0.0004 M.

To determine the hydroxide ion concentration in a solution of HCl, you need to consider the dissociation of HCl in water. HCl is a strong acid, which means it completely dissociates into its ions in water. The balanced equation for the dissociation of HCl in water is:

HCl(aq) → H+(aq) + Cl-(aq)

Since HCl is a strong acid, it only donates H+ ions to the solution and does not yield any OH- ions directly. Therefore, the hydroxide ion concentration in the solution can be calculated indirectly by considering the behavior of water.

In pure water, the concentration of both H+ and OH- ions is assumed to be 1.0 x 10^-7 M. This is because water undergoes autoprotolysis, where it acts both as an acid and a base, resulting in the formation of equal concentrations of H+ and OH- ions:

H2O(l) ↔ H+(aq) + OH-(aq)

However, when we add a strong acid like HCl to water, the concentration of H+ ions increases significantly, while the concentration of OH- ions decreases. In this case, the H+ ion concentration dominates, and the OH- ion concentration can be considered negligible.

Therefore, for a solution of 0.0004 M HCl, the hydroxide ion concentration ([OH-]) can be considered negligible. It is important to note that the hydroxide ion concentration in this case does not actually equal to zero, but it is so small compared to the H+ ion concentration that it can be neglected for practical purposes.

So, in this specific case, you do not need to use the pOH^- = -log[OH^-] formula, as the concentration of OH- is negligible. Instead, you can just report that the hydroxide ion concentration in the solution is essentially 0 M.