A 100.0 mL sample of a solution that is 0.100 M in HCl and 0.100 M in HCN is titrated with 0.100 M NaOH. Calculate the pH after the addition of the following volumes of NaOH:

(a) 0.0 mL

Video transcript

Welcome back everyone. A solution containing 0.150 molar hydrochloric acid and 0.202 folic acid is titrated with 0.150 molar sodium hydroxide, determine the initial ph of the solution before the addition of sodium hydroxide. If we're considering the initial solution before the addition of sodium hydroxide, that means we have two components. HCL and HF and those are two acids to begin with. HCL is a strong acid and upon its ionization, it releases the same quantity of hydro num, right based on stom Mery and based on the fact that it is a strong acid for Hydrofluoric acid, it is a weak acid and it only partially ionizes to release a negligible quantity of H 30 plus. In addition to that the common iron effect dictates that the strong acid will essentially allow us to release even lower amount of hydro num from the weak acid. Meaning H 30 plus coming from the strong acid is the predominant quantity and H 30 plus coming from HF is negligible based on the common iron effect, meaning we can ignore it. First of all, the reason why we can ignore it is simply because even without the common eye and effect is 0.200 molar of HF would release a very small quantity of hydro. But since HCL is already present in the solution, where we release 0.150 molar of hydro num. Based on the complete ionization of hydrochloric acid, we can completely neglect the additional quantity of hydro coming from Hydrofluoric acid. It will be completely negligible for the total quantity of hydro num. And now that we have shown that the total quantity of hydro is approximately equal to 0.150 molar, which is the initial concentration of HCL. We can sell that our P based on the formula is equal to the negative log of the concentration of hydro which is 0.150 molar. If we evaluate the result, we get the ph value of 0.8233. Our final answer, it's independent of the concentration of sodium hydroxide because we haven't added any base yet. Thank you for watching.