On the same graph, sketch pH titration curves for the titra-tion of (1) a strong acid with a strong base and (2) a weak acid with a strong base. How do the two curves differ with respect to the following? (a) The initial pH

Video transcript

Hello. Everyone in this video, we want to draw the peach curves for a strong acid based situation and a weak acid based filtration on the same exact graph and based on the graph, which statement is true regarding their initial ph Alright, so the an elite here is a strong So if we have a strong acid based situation, let's write this out so strong. I just simplify that too. Strong are an elite. Here is a strong acid and the tight trahant is a strong base. So first initially initial meaning before addition of basis added. Only the strong acid, so S. A. Is present and the ph of course is then acidic then too after base. So basically after the addition of base. But before the equivalence point here, the moles of our strong acid is going to be so greater than the moles of our strong base and some acid is converted into conjugate base or its respective conjugate base. At .3 here, the Ph is going to be acidic. So at halfway this is halfway so half of equivalence point, So E. Q point, the moles of the strong base added. Is it equal to have the moles of their acid? Again, we always said that ph is acidic. Now .4 Here, at the equivalence point, the moles of our strong base is equal to the molds of the strong acid and here are PhD N is equal to seven and .5.5 is just after the equivalence point. So at this point then the most of our strong base is greater than the most of our strong acid here, all of all of the strong acid has been consumed and only the strong base is present. And if only the strong base is present, then of course our ph is going to be a basic one. So this is what goes on in a strong acid, strong based filtration. Now, let's take some notes here regarding our weak acid and strong based his creation. That's all for this one. We'll just put weak. So let's just go down here for more space. So for our week, acid and strong based situation, the analytics is going to be a weak acid. And for the titans it's the same. We still have a strong base. Alright, so .1 here, this is initial, the initial point of course, meaning before the addition of base. So at this point here only the acid is present. So this means of course our ph then is still acidic, even though we have a weak acid is still going to be acidic. Now that points to this is after the addition of base. But of course still before the equivalence point. So at this point, the mole of our weak acid is so clear than the molds of our strong base. We know that some acid is converted to the conjugate base or the respective conjugate base. And here at this point the P H is still acidic, Then moving on to step three. This is at the halfway point of the equivalence point here, our moles of strong base added is equal to half of the moles of acid and the ph here is still going to be acidic At .4. Here, this is at the equivalence point. So at this point then the mold of strong base is equal to the moles of our weak acid. So here all of the weak acid is converted to its perspective, conjugate base. And at this point our p is going to be greater than seven. So as final .5, this is after the equivalence point, the moles of strong base is greater than the moles of strong acid At this point at this point, all of the weak acid has been converted and too strong are its perspective conjugate base and we have an axis of our strong face, which then this means our ph is going to be basic. Alright, so, initially the strong acid and strong based situation only has a strong acid And for the weak acid and strong based situation, it also has the weak acid. The strong acid has a lower ph than the weak acid. For the initial solution of page strong acid, strong base situation is going to be less than the ph of the weak acid and strong based situation. So this can be definitely a huge point that we can look for in our answer choices. So we see here we have answer choice A, B, C, D, E and F. And we said that the strong acid, strong base saturation ph is less. So we need to look for that here. If we look for that and our answer choice, we see that the only one that has this criteria is going to be extra choice A where it says that the weak acid has a higher initial P. H. So this right here is going to be my final answer for this problem.