Calculate the pOH of a 15 mL sample of 0.76 mol/L hydrosulfuric acid given that it only dissosiates 92% in solution.
I assume you mean (H^+) = 0.76 x 0.92 = ?
Convert that to pH, then to pOH.
Ms Lena, the 92% dissociation for H₂S (hydrosulfuric acid)* is quiet high for an acid with a Kₐ₁ = 8.9E-8*. (*Ebbing's Gen Chem; 11th Edn.) I calculate the %ionization for a 0.76M H₂S solution to be ~0.034%. Never the less, a 0.76M H₂S solution would have a hydronium ion concentration of 2.6E-4M giving a pH of 3.58. pOH = 14 - pH = 14 - 3.58 = 10.42.
[H⁺]* = SqrRt(Acid Concentration x Ka-value)
*Assuming all of the H⁺ comes from the 1st ionization step as the 2nd ionization step would deliver [H⁺] ~ 1oˉ¹³M range (negligible).
%Izn = [H⁺]/[H₂S] x 100% = (2.6E-4/0.76)100% = 0.034% w/w
Just for consideration, if H₂S were 92% dissociated, then [H⁺] =0.92(0.76M) = 0.6992M => pH = 0.16. This is in the range of very strong acids that ionize 100%. HCl, HBr, HI, HNO₃, HClO₄ & H₂SO₄. Weak acids with Ka-values in the 10ˉ⁵ to 10ˉ¹⁰ range typically have pH values in the 3 to 4 range at ambient conditions.
**hydrosulfuric acid => h ttps://socratic.org/questions/what-is-the-formula-for-hydrosulfuric-acid => H2S
To calculate the pOH of a solution, we need to determine the hydroxide ion concentration ([OH-]). Given that the hydrosulfuric acid solution only dissociates 92%, we can assume that 92% of the originally supplied hydrosulfuric acid will dissociate into hydrogen ions (H+) and hydroxide ions (OH-).
Step 1: Calculate the concentration of hydroxide ions ([OH-]) after dissociation.
- Since hydrosulfuric acid (H2S) dissociates into two ions (H+ and HS-), and 92% of the H2S dissociates, we can find the concentration of HS- ions.
- The concentration of HS- ions = 0.92 * 0.76 mol/L = 0.6992 mol/L
- Since H2S is a weak acid, we assume that the concentration of H+ is negligible compared to HS-.
- Therefore, the concentration of OH- ions will be equal to the concentration of HS- ions in this case.
Step 2: Calculate the pOH using the concentration of hydroxide ions ([OH-]).
- pOH is the negative logarithm (base 10) of the hydroxide ion concentration ([OH-]).
- pOH = -log10([OH-])
Let's plug in the values and calculate the pOH:
- [OH-] = 0.6992 mol/L
- pOH = -log10(0.6992)
Using a scientific calculator, we find that the pOH is approximately 0.154.
Therefore, the pOH of the 15 mL sample of 0.76 mol/L hydrosulfuric acid, assuming 92% dissociation, is approximately 0.154.