Concentration of Solution Formulas

in today's lesson I'm going to give you list of formulas that will help you to calculate the various concentrations of solutions for those of you who might be studying this topic in school for so for the first type of concentration that you need to be familiar with is mass percent mass percent is basically the mass of the solute div div by the mass of the entire solution time 100% so that's how you can calculate mass percent with regard to Solutions now it's important to understand that the solute plus the solvent makes up the solution so if we think of salt water solution Sodium Chloride will be the solute that's the salt the solvent dissolves the solute so water will be the solvent combined the salt water that mixture is the solution so it's important to distinguish the solute the solvent and the solution when using these formulas now the next Formula you need to be familiar with is volume percent so instead of taking the mass of the solute we're going to have the volume of the solute on top and on the bottom it's going to be the volume of the solution time 100% so that's how you can calculate volume percent the next form of concentration is mole fraction mole fraction or at least the mole fraction of is equal to the moles of / the total moles in the solution and the total moles will be the moles of all the substances in the solution so NB and this could can continue depending on how many different substances are in the solution now the next form of concentration is marity represented by capital marity is basically equal to the mole of solute ID the of solution you can also write it this way will typically represent moles of solute and is the volume similar to marity is mality mality like marity is equal to the moles of solute but here is where it differs instead of dividing it by the liters of solution you need to divide it by the kilogram of solvent so marity is moles over volume mality is moles over the mass in kilog of solvent typically when write lowercase usually write it in terms of mass and grams now the next one is normality there's lot of formulas for normality here's simplified version of it normality is the mass of the solute in time this is not moles by the way so to give you an example of what this represents for acids is the number of hydrogen ions per formula unit so for HCL is one for sulfuric acid we have two protons per formula unit and is two for bases it's the number of hydroxide ions per formula unit so for calcium hydroxide would be two so for this formula just make sure you know that this is not the same as moles so it's the mass of solute time / the volume the volume is the lers of solution times the molecular weight or the molar mass of the solute now if you know the marity of the solution you can calculate the normality but first i'm going to rearrange this equation so here we have mass over molar mass so this is the mass of the solute divid by the mol mass of the solute and then we have on the bottom and then we have this now this part right here mass of solute divided by the mol mass of the solute that's basically the moles of the solute that's this part this part here the volume that's basically the lers of solution and then kept this on the outside now we know that moles of solute divided lers of solution is marity so normality is basically the marity time so for instance let's say if have three molar h2so4 solution and want to calculate the normality the marity is three and there's two protons per formula unit so the normality is going to be six let's say for instance have four mol HCL solution the normality is going to be four because we only have one proton performal unit so let's say if have five molar phosphoric acid solution and all of the protons are going to be consumed in the reaction the normality is going to be 5 * 3 which will be 15 so the normality will be three times as much so that's how you can use this formula to calculate the normality of solution if you know the marity now when you see Parts PPM this is parts per million it's another form of concentration now PPM could be represented in Mass over mass volume over volume or mass over volume for Mass over Mass we're going to have the mass of the solute divided by the mass of the solution and since this is parts per million 1 million is 10 6 so it's going to betimes 10 6 ppb is parts per billion instead of over I'm going to use over just to change it up so if you see over you're going to have the volume of the solute ID by the volume of the solution now because both of these are mass the units can be anything they just have to match so if your mass of solute is in grams the mass of the solution has to be in grams because they're going to cancel if the mass of solute is in milligrams the mass of the solution is in milligrams same thing for this formula they need to match as well it could be milliliters and milliliters or liters and liters now since we're do with parts per billion this needs to be 10 to the knot if you see PPT you might be dealing with parts per trillion I've RAR seen parts per thousand but if it's parts per trillion then this would be 10^ 12 now PPM let's write the formula for over so this is mass over volume so we're going to have the mass of the solute divided by the volume of the solution now since it's parts per million PPM this is going to be 10 6 now since these are two different things they have different units they won't cancel you need to be careful with the units so for this particular formula the mass of the solute must be in and the volume has to be in Mill when it's like that this number will be 6 now there's another variation of that formula if you put the mass in milligram and the volume in liters you won't need the 10 to the 6 number it'll automatically give you the concentration in parts per million the reason for that is 1 PPM is equal to 1 mg per liter so if you have those units you won't need the 10^ the 6 multiplication Factor however if you put mass in grams and the volume in milliliters to get the right answer you need to include the 10^ the six Factor but if you use these units you won't need to multiply by 10 the 6 so it's important to understand that if you're using the overv calculation now for one part per billion that's equal to 1 microgram per liter so if you use micrograms here and laders there you're not going to get PPM you're going to get ppb due to this equality so you may want to add this to your notes and of course you can get all of this in formula sheet that I'm going to post in in the description section below now have some other formulas in that formula sheet that didn't cover in this video so once you download it you'll see the other formulas that didn't talk about in that formula sheet so that's going to be it for this video thanks again for watching