A 100.0-mL buffer solution is 0.175 M in HClO and 0.150 M in NaClO. b. What is the pH after addition of 150.0 mg of HBr?

Video transcript

Hello. In this problem, we are told we have 0.125 bola hydro sonic acid and 0.14 Mueller sodium cyanide mixed to produce 100 25 mL of buffer solution were asked to determine the ph of the solution. If 100 25 mg of hydrochloric acid was added for given the acid dissociation constant, then for hydrostatic acid. So let's begin by then determining what makes up our buffer solution. So we have hydro sonic acid which is a weak acid. They will go undergo hydraulic sis, so it will donate a proton water, perform cyanide and had joining mines. So the cyanide is the conjugate base then of our weak acid. When we have both the weak acid and its conjugate base, we form a buffer solution and so the cyanide then comes from the sodium cyanide. In our next step, then let's find the concentration of hydrogen ions that are added with the addition of hydrochloric acid. So we have 100 25 Milligrams of hydrochloric acid added to 125 ml of solution. When we have milligrams over milliliters, the mila cancels and we're left with grams per liter. We can then convert our mass to moles Using the more mass of hydrochloric acid. One more hydrochloric acid has amassed 36.46, 1 g and so are grams of hydrochloric acid cancels and one more of Hydrofluoric acid will produce one more Of hydro nines are moles of hydrochloric acid cancels the concentration of our hydro nines and 0.0274 moller. And next step then is determined concentration of cyanide and hydro sonic acid. After the addition of the hydrogen ions from the hydrochloric acid. So we'll write an equation. So our conjugate base then is going to be the component that reacts with the hydro lines and we'll farm hydro sonic acid, We have initial change and final. So initially the concentration of cyanide is . That of our hydro 9 0.0274 and that of our acid is 0.125. So assume that all of the hydrogen ions react. Given that the story geometry is 1 to 1. That means an equal amount of cyanide will react and an equal amount of our acid will be produced so Final. Then all of the hydrogen ions have reacted to that. zero. The amount of cyanide will be 0.1126 and that of our asset is 0.15-4. Given that we have a buffer, then we can make use of the Henderson Hasselbach equation to calculate the ph and the Henderson has back equation and tells us the ph is equal to the P. K. A. Plus the blog of our get base concentration. So that's our cyanide, all over that of our acid ph sen is the negative log of our acid association constant which is 4.90 times 10 to the minus 10 for hydro sonic acid and then log of the concentration of our base, which, from the table tells us, is 100.1126, divided by that for the acid, which is 0.15 to four. So our ph then works out to 9.178. This ph then corresponds to answer a thanks for watching. Hope. This helps.