Consider the titration of a 35.0-mL sample of 0.175 M HBr with 0.200 M KOH. Determine each quantity. a. the initial pH

Video transcript

Welcome back everyone to another video. Consider the titration of a 56 mL sample of 0.745 molar hydro Bromma acid with 0.210 molar potassium hydroxide, determine each quantity a the initial ph and were given for answer choices. A 2.43 B 0.175 C 1.98 ND 0.128. Let's begin by understanding that we don't need to use the information given to us regarding potassium hydroxide. Why? Well, essentially in this problem, hydroponic acid is our analy. It's something that we titrate and potassium hydroxide is our tit trend. So essentially what that means is that if we're looking for the initial ph, then we haven't yet added our tigh trend and we only analyze our analy. So initially, we only have hydroponic acid in our flask and we have to remember that it's a strong acid, which means that it ionizes completely in the water. So we have our proton transfer from H pr to water and we are producing hydro which is responsible for the acidic medium and the bromide anion, which is our conjugate base because it's a strong acid according to stir geometry. If we start with 0.745 molar, then we release an equivalent amount of hydro. Let's recall that th is equal to the negative log of the concentration of hydro. And in this case, we know that the concentration of hydro is 0.745. So if we do the math, we end up with 0.128 as our ph therefore, the correct answer to this problem is option D 0.128. Thank you for watching.