In addition to the acid-dissociation constant, Kappa a, another measure of the s

Question

In addition to the acid-dissociation constant, Kappa a, another measure of the strength of an acid is percent ionization, determined by the following formula: Percent ionization = Percent ionization increases with increasing Kappa a. Strong acids, for which K& is very large, ionize completely (100%). For weak acids, the percent ionization changes with concentration. The more diluted the acid is, the greater percent ionization. A certain weak acid, HA. has a Kappa a value of 8.5 times 10-7. Calculate the percent ionization of HA in a 0.10 M solution. Calculate the percent ionization of HA in a 0.010 M solution Plusminus pH of a Strong Acid, a Weak Acid, a Strong Base, and a Weak Base The pH of a solution is the negative logarithm of the molar concentration of hydronium ion, that is, pH = -log[H3O+] In neutral solutions at 25 degree C, [H3O+] = 10"7 M and pH = 7. As [H30+] increases, pH decreases, so acidic solutions have a pH of less than 7. Basic solutions have a pH greater than 7. The hydroxide and hydronium ion concentrations are related by the the ion-product constant of water, Kw, as follows: Kappa w = 1.0 x 10-14 = [H3O+][OH-] In the same way as the pH, we can define the pOH as pOH = - log[OH-]. It follows from the Kw expression that pH + pOH = 14. Assuming equal concentrations, rank the following aqueous solutions in order of decreasing pH.

Explanation / Answer

8A) KA = 8.5*10^-7 That means that for the reaction HA H+ + A-, [H+][A-] / [HA] = 8.5*10^-7 If we let x be the amount that is ionized, this gives us the equation: x^2/(0.10 - x) = 8.5*10^-7 We can then solve for x to get: x=2.92*10^-4 M So, [H+] =2.92*10^-4 M Now, we can divide [H+] by the initial acid concentration to get percent ionization. 2.92*10^-4 M / 0.10 M * 100 = 0.29 % 8B) This time we solve the equation x^2/(0.010 - x) = 8.5*10^-7 That is: x = 9.18*10^-5 So dividing that by the original concentration gives us: 0.92% 9A) HCl is the strongest acid Then HOCl Then N2H4 Depending on the concentration of the solution, NaOH may be a stronger base, than Ba(OH)2, or they may be tied. There is no way to tell without them giving an actual concentration. So the answer is: NaOH,Ba(OH)2, N2H4, HOCl, HCl

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