Calculate the pH of a solution made by adding 2.50 g of lithium oxide 1Li2O2 to enough water to make 1.500 L of solution.

Video transcript

Hello everyone. So in this video we're trying to solve for the ph of a solution that is containing the calcium oxide and H 20. So water. So first thing I want to go ahead and do is to go ahead and write out the chemical equation again. We have the calcium oxide Which is a solid state directing with H 20. Which is a liquid. What we get here on the product side is the calcium ion which is a quiz. And two moles of our hydroxide ions. Again that is going to be Aquarius. So once we have that we can go ahead and start our dimensional analysis. So I'm gonna go ahead and start off first with the given mass of calcium oxide. So that's 1.15 g of C. A. O. I'm gonna go ahead and want to convert that grams into moles. We can do that using the molar mass of calcium oxide. So for every one mole of calcium oxide we will have 56.78 g of calcium oxide. We can see here that the grams will go ahead and cancel out. Next. I'm gonna go ahead and use my chemical equation and use their geometry techniques to go ahead and sell for the moles of O. H. So we see that the ratio is for every one mole of calcium oxide. We have two moles of R. O. H minus. And again you can see that the moles of calcium oxide will cancel leaving us with the units of moles of hydroxide. So putting those values into my calculator I would get the value of 0. moles of my hydroxide and ions. And my concentration of my O. H. And remember that the units of concentration is of course moles per liter. We just saw vermin mold. So we'll put that on top 0. moles of my O. H. And the um leaders are volume of my solution is given to us in the problem that is 2.25 L. Putting this into my calculator. I would get that. The concentration of my hydroxide is 0. moller. Alright so next step here we know that are kw value is equal to the concentration of R. H. Plus multiplied by the concentration of R. O. H minus. And that is of at standard conditions. 1.0 times 10 to the negative 14. We have just solved for the concentration of O. H. So we can go ahead and actually plug that in. So H plus multiplied by 0.01822858. You're going to 1.0 times 10 to the -14. We need to go ahead and isolate this concentration of age plus. So divide both sides by this big number here. So if I put that into my calculator. Then I'll get that the concentration of my age plus is equal to 5. oh eight times 10 to the negative 13 moller again scrolling down to give us a little more space here. We can now use this value to go ahead and sell for our peach. If we recall the equation for P. H. Is the negative log of the concentration of our H. Plus, which is what we just offer. So P. H. is equal to the negative log of 5. times 10 to the -13. So putting that into my calculator, I can see that my P. H. is equal to 12.261. And this right here is going to be my final answer for this problem. Thank you all so much for watching.