right so this is a video on acids bases and pH it's going to concentrate mostly on astrally and pH with bases and kW the dissociation the Onix Association of water for constant come up in a separate one so I'm gonna concentrate on acids and pH but I will mention bases at the start as is my new little thing I'm going to any of these notes I'm going to put this in the little description and if you want to download this and use this as notes you're more than welcome to a few bit of us in the past so yeah ok acids and bases definition so I'm gonna I'm not gonna bother with Lewis acids and bases wasn't that sort of benefited to a different topic where looks better later in unit five it would be right now as I'm doing this in the future it'd win a different unit as we go into the year two of the AQI stuff all very confusing but it fits better in some of the complex ions stuff for transition metal things so the definitions I'm looking at is that the bronsted-lowry definition and so bronsted a bit fine that pen really isn't it let's let's unfine it though yeah so the bronsted-lowry definitions of acids and bases are that our acid is a proton donor so hopefully can be quite quick the video really that's my new thing short videos and a base is in sort of simple terms a proton acceptor and you get various questions where they basically give you a situation they'll ask you what's the acid what's the base and all the rest one could be let's have a think trying to think of one that i can think of here you could equation for each one to show the idea of the of an acid and a base i guess we could we could have some like nh3 h+ becoming NH four plus we can see that in the process of going as the reaction takes place the the ammonia gains the H+ ion therefore becoming the ammonium ion so that's acting as a base clearly acting as a base an acid we could have something like I guess we could do a reaction like this which probably pinpoint some of it as balance yep yep so in this case here what we've got is the idea of the hydrochloric acid donating its proton to the water therefore acting as an acid proton donor the water on the other hand here has accepted a proton water can act as an acid or a base depends on the situation but it's accepted the proton becoming this hydroxyl ion here the h3o plus therefore acting as a base so acid base in this case you these kind of questions do come up but they're less less common and a quite straightforward when it provided you know this definition of proton donor and proton acceptor for acids and base respectively you shouldn't have any real issue kind of working out what's going where just look literally what where the protons or the hydrogens really have gone to they've left this one therefore this has to be acid they've gone to this one therefore this must be the base and obvious another one there little bit there I'm not going to touch on bases anymore they're there they're going to come up in a different video I'm going to concentrate on this point on acids and pH and this term pH is quite a nice one pH certainly the people I guess you look up to clean school and things from prolly about year seven you look at what the terms pH what the term pH means I should say it's people normally quite sort quite comfortable I guess to the idea of pH as having PHS assets having low PHS bases or alkalis having high pH and neutral being around this or middle area off of seven and those those are the numbers we tend to associate with pH as well normally we would go from 1 to 14 is it sort of the junior school lower down junior end of senior school the numbers associate but we the numbers really can't be much saw less and greater than that we can have negative ph's and really the scale that's better to use I suppose it's still very simplistic would be a scale of zero to fourteen just to highlight something that I'm going to look at in a second so this scale cancer can go into - figures and it can go greater than fourteen it just tends to be a sort of a nice scale that we can use where we can put things on here we can say that this is the strong acid this is the strong base or strong alkali neutrals in the middle and all the rest and all pH is its it's a simplified scale it's a logarithmic scale it takes a very very wide range numbers the numbers are if we're dealing with sort that has a pH of 0 pH by the way is just a relation to the concentration of hydrogen ions I'll define this property in a second so if we said that a solution has a hydrogen ion concentration of 1 mole per decimeter cubed we would set has a pH of 0 if on this hand though as a pH of 14 that means as a concentration of 1 times 10 to the minus 14 mole per decimeter cubed and we can see that's a vast range of numbers there's a huge difference between 1 and 1 times 10 to minus 14 where it's actually when we look at the pH scale 0 to 14 very manageable very easy to deal with so the pH scale is very very useful and we can convert these numbers into ph's and we can convert the pH is into the actual concentrations because it's a log scale pH basically the basic limit base at pH is equal to the minus log of the hydrogen ion concentration so square brackets equals concentration in moles per decimeter cubed so minus log of the hydrogen ion concentration it's literally a case if you've got a hydrogen ion concentration you put it in here you minus log it and you get an out to the pH so if you put one into here right now and you do minus log of one you will get zero if you do minus log of 1 times 10 to the minus 14 you will get 14 it's as is that very very straightforward this is a definition of pH okay that there is a definition of pH you don't need to worry about it doing it in word format you are more than welcome just to do it as pH equals minus log of the hydrogen ion concentration square brackets and all the rest you've got out of that there cuz if it's normal brackets it's not denote in the the concentration of but if you write that in the exam you're going to get one mark that's quite nice you can flip this around slightly and those of you who are who are matha see unlike me you can work out the hydrogen ion concentration from the pH and that is apparently as simple as saying 10 to the power of minus pH and again you could put these numbers in and you could do 10 to the power of 0 basically minus zero and you would come out with one there as your answer nice and again one time Center miles 14 and all the various bits in between bear in mind we don't have to have one time Center months 14 we could have one point six seven times in the months 14 you know and all these other horrible numbers in between so how would you in an exam we're going to come across so I'm not going to do any exam questions on this one because they tend to come into the grand scheme of things with with more vests and bases this is more of a kind of a real introductory one hopefully quite quick although I do tend to go on so what you might get in an exam I'm gonna give the resore questions I'll write out first and you can then check if you've got it right if you want to go ahead you can do so you could get you could be asked to find the pH of the following naught point one five more breaths meter cubed and I'll run through each one in term so what's the pH of that now either you pause that and then are now waiting for me to work it out or you're just waiting for me either way it doesn't matter what the way I tend to do this is I took the first of all look at the dissociation here that's occurring so we've got strong acids okay we'll look at weak acids a separate video but strong has to dissociate in this way and it's a bit of a simplified format but it kind of works it's very similar to this bit up here with my hydronium R but it's a nice simplified version where I've not included water I think just makes it a little bit more straightforward so key thing is my hydrochloric acid my hydrogen chloride molecule dissociates in water to give me one H+ ion and one chloride arm and that's very important because the dissociation is one-to-one which means the concentration therefore of hydrogen ions is not 0.15 so pH is minus log of not 0.15 now and after use square brackets because I'm putting an actual value in minus log naught point five it's going to be naught point eight two now important point to note here are not the change color two decimal places always always give your answers for pH to two decimal places they'll normally specify in a question always two different places obviously rounded correctly whenever this was a common break salable this was now a naught point eight to one for example rounded to naught point eight two if it was a naught point eight to five nor point eight three would be my answer so round correctly and do it to two decimal places please we have another one this isn't this is a good example for the reason that I almost gave away then but I don't know don't ruin it do make sure we sit the minus in as well don't don't get messed up with that one okay do pertain nitric acid two point six four mole per decimeter cubed nitric acid pause and do it I don't know or you just listen to me whatever again the dissociation hno3 to h+ and no.3 - so same thing before it's one to one giveaway here is the fact that we've got the H there only one H splitting boom right down there the same thing concentration was two point six four means this is going to have a concentration of two point six four as well so we go PHS - log of two point six four and we get an answer of this time - nor point four - so very much just a logarithmic scale doesn't mean there's actually negative ions is not there's obviously a very high number of ions actually but the fact it's logarithmic makes it Emeline us again two decimal places very very important and finally last but not least this will be the end of the video after this one 0.315 mole bliss meter cube solution of sulfuric acid pause and do things okay slight tricky and they like to use these examples again with the basis as well which I'll look at in a different video they light up tickling my throat they like to use this case what we call a diprotic acid for good reason and that's because when we have h2 so4 we find that it dissociates into two h+ and an so4 2 minus therefore my concentration of h+ in this case is not 0.315 looking at the ratio 1 to 2 nor point 3 1 5 times 2 therefore nine point six three oh but then the calculation is the same it's the minus log of naught point six three oh and that gives us a value of naught point two zero it's what lovely numbers these are three calculations they're looking at calculating the pH bit of definition of the acid term acid in term base bit of linking it to a sum equation ah'd a huge amount there because you could go on all day looking at various equations but rhiness about practicing and making sure you're happy with where the s and the base is but it's also do these definitions obviously dissociation here i think it's a key one because it really helps you work out where your what your concentration is going to be particularly here we put a double besides up that's basically your base is little bit of what a little bit bases acids and your ph calculations which then span into all these other topics of acids and bases any problems comment remember you can download these notes if you wish otherwise good luck with those