The probe of the pH meter shown here is sitting in a beaker that contains a clear liquid. You are told the liquid is pure water, a solution of HCl(aq), or a solution of KOH(aq). (b) If the liquid is one of the solutions, what is its molarity?

Video transcript

Hey everyone, we're told that the ph of a colorless solution was measured using a ph meter as shown below. Is this a solution of hydrochloric acid or a solution of sodium hydroxide. What is the modularity of the solution? If the liquid is one of these solutions First, let's go ahead and assess our image here. We can see that we have a ph of 12.85, which means that we are strongly basic and because we are strongly basic, this must mean that we have sodium hydroxide as our solution since hydrochloric acid is an acid and sodium hydroxide is a base. Now, in order to calculate the polarity, we need to calculate the concentration of our hydroxide ions at approximately 25 degrees Celsius. In order to do so, we first have to determine our P. O. H. Now we know that our ph plus our P O. H equals 14 To determine our P. O. H. We can simply subtract ph from our 14. So since our image told us that our ph is 12.85, we can plug in that value into this equation And we end up with a p. o. h of 1.15. Now, to calculate the concentration of our hydroxide ions, we're going to take 10 to the negative P. O. H. So plugging in that value, we get 10 to the negative 1.15. And when we plug this into our calculator, we end up with a polarity of 0.071 molar. And this is going to be our final answer. Now, I hope that made sense and let us know if you have any questions.