Determine the pH of a solution that is 3.85% KOH by mass. Assume that the solution has density of 1.01 g>mL.

Video transcript

Hey everyone, we're asked to calculate the ph of a 2.31% by mass solution of sodium hydroxide. The density of the solution is 1.2 g per millimeter. So since we have a percentage here, we're going to go ahead and assume that we have 100 g of our solution. Now we can go ahead and calculate the concentration of our sodium hydroxide And we can do so by taking our 2. g of sodium hydroxide per 100 g of solution. And we're going to use dimensional analysis here. So using sodium hydroxide molar mass, we know that we have 39.997g of sodium hydroxide per one mole Of sodium hydroxide. Using the density of our solution, we know that we have 1.02 g per one millim. And lastly we want to convert our milliliters into leaders and we know that we have 10 to the third milliliters per one liter. Now, when we calculate this out and cancel out all of our units, We end up with polarity of 0.58909 moller of sodium hydroxide. Now we know that sodium hydroxide is a strong base and this means that it dissociates completely. So we can go ahead and say that the concentration of our hydroxide ion is the same as the concentration of our sodium hydroxide initially and this is equal to 0.58909 moller. So we can use this value to calculate our P. O. H. By taking the negative log of the concentration of our hydroxide ion. In this case it will be 0.58909. And this will get us to a po h of 0.23. But since our question asked us to calculate for the ph we know that our ph is going to be equal to 14 minus our p o. H, which is 0.23. So this gets us to a ph of 13.77, which is going to be our final answer. Now. I hope this made sense and let us know if you have any questions.