 So I guess the first thing to say about these is there's three examples in this video You can have a look at them all together or one at a time feel free to pause the video Perhaps even turn down the sound and just watch the process see if you can calculate the answers to each of these as I do them And see if we get the same answers and if you don't let me know We can always check and make sure that we haven't made any silly mistakes along the way So the first thing that we want to do is we want to have a look at what happens to the pH of a solution after it's been diluted So here we have Some nitric acid HNO3 in solution We know that the initial volume of the solution is five mils and I'm already going to convert that to point zero zero five liters Only because I know that if I'm looking at concentrations in moles per liter I'm going to have to get that back to liters just for consistency sake so you can see I've also got an initial Concentration, which is equal to point zero one moles per liter then what I'm going to do is I'm going to dilute this to a 100 mil solution so my final volume is Equal to be is going to be equal to be one hundred mils Which is going to be point one? liters and I need to calculate the pH of the dilute solution So in order to calculate the pH of the dilute solution, we need to use our formula Which is that pH is minus the log base 10 of the concentration of hydrogen ions So I need the concentration of hydrogen ions to do this question I also know that because I'm dealing with nitric acid. It's a mono protic acid So therefore if I just move it over here a little bit I know that when it ionizes in water, and I'll just simplify this a little bit to H plus ions and NO3 minus ions and of course they're aqueous The important thing is the mole ratio is going to be one to one now if I include water Which is a better way of doing it. I'm just a little bit cramped for space The ratio will still be one to one and the form of the hydrogen will be the hydronium ion H3O plus and that's fine So what I need is this concentration So what I want to know is what is the final concentration of the solution and then that's what I'm going to plug into my equation So in order for me to do that. I'm going to need to Have to find the relationship between the initial solution and the final solution Now I know that I always put my name on my CV So the number of moles is equal to the concentration multiplied by the volume Now one of the important things about this is if I look at the initial number of moles I can multiply the initial concentration by the initial volume But I'm also aware that I haven't actually added any of my Acid during the dilution. I've only added water So therefore the number of moles initially is the same as the number of moles finally So these two values are the same and what that means is that the C initial the Initial is equal to C final the final because I just put these two equal to each other Because I don't know the final one if I divide both sides by vf I'm going to be able to find the final concentration is going to be the initial concentration 0.01 multiplied by the initial volume, which is 0.005 And then I'm going to divide all of that by 0.1, which is my final volume And that is going to give me and I'll just pop this on the calculator so 0.01 times 0.005 and then divided by 0.1 is going to give me a value of 5 times 10 to the minus 4 moles per liter To find my pH then I put that value in so pH is equal to minus the log base 10 of 5 times 10 to the minus 4 and that's going to give me a pH value of 0.3. It's hard on these little slides to set these things out Vertically and make sure that you have everything neat and tidy and it and it doesn't really matter at this point as much Whether you can get to the right solution It's obviously better if you can but that you make sure that your sequence is easy for a market to follow that they know What formulas you've used what values you've used and if you have made a mistake anywhere as I may have I can go back in and check Anywhere along the line where my initial values correct where my final values correct What assumptions did I make about what was going to be used? How did I rearrange the equations in order to try and solve the problem? substitute my values find my initial Number and then use that number to calculate my final result. So setting your workout is really really important