The pKa for hydrochloric acid is −6.0.
What is the concentration of HCl(aq) we
would expect to find in a 1 M solution of
hydrochloric acid? What pH would we
expect?
how do you solve this problem?
To solve this problem, we need to use the relationship between pKa, pH, and concentration. The pKa value is the negative logarithm (base 10) of the acid dissociation constant (Ka).
First, let's find the concentration of HCl(aq) in a 1 M solution. We know that the pKa of hydrochloric acid is -6.0, so we can use the formula: pKa = -log10(Ka). Rearranging the equation, we get Ka = 10^(−pKa).
Substituting the given pKa value of -6.0 into the equation, we get: Ka = 10^(−(−6.0)). That simplifies to: Ka = 10^6.0.
Next, we'll use the equation for Ka to find the concentration of HCl(aq) in a 1 M solution. The Ka expression for a weak acid HA dissociating into its ions is: Ka = [H+][A-] / [HA]. In the case of HCl, which is a strong acid, it dissociates completely into H+ and Cl- ions, so the concentration of H+ is equal to the initial concentration of HCl.
Since we're looking for the concentration of HCl in a 1 M solution, we can conclude that the concentration of HCl is also 1 M.
Now, let's determine the pH of this solution. pH is calculated as the negative logarithm (base 10) of the hydrogen ion concentration ([H+]). In this case, the concentration of H+ (which is equal to the concentration of HCl) is 1 M.
So, using the formula: pH = -log10[H+], we can substitute [H+] = 1 M, and find the pH: pH = -log10(1) = 0.
Therefore, we would expect to find a concentration of 1 M HCl(aq) in a 1 M solution of hydrochloric acid, and the pH of the solution would be 0.