'Tris' is a buffer often used in biochemistry. We can...

'Tris' is a buffer often used in biochemistry. We can simplify the equilibrium reaction as Tris·HCl+H2O ? Cl- + H3O+ + Tris with pKa = 8.072 and the molar weights m(Tris)=121.135 g/mol and m(Tris·HCl)=157.596 g/mol. a) What is the pH of a 1L solution made from 12.43 g of Tris and 4.67 g Tris·HCl? b) What is the pH if you add 12 mL of 1M HCl to the solution prepared under a).

Transcript

00:01 Hello students welcome here in this question tris is given so tris is a buffer which is also known as trace aminomethane is another name so here the equilibrium reaction is given for this one so tris hcl plus h2o gives rise to tris plus cl minus plus h3o plus is a equilibrium reaction so here we have pka value is given 8 .072 and the molar mass of tris is given so for tris the molar mass is 121 .135 and for tris hcl it is 157 .59 is a grams per molar mass so then we will calculate we have to calculate the ph value for this these values so this tris okay this solution buffer solution so here we know that ph of the solution is equal to pka plus lock here it is tris is a buffer divided by acid here tris is here okay so here we have to calculate the concentration of tris here they are given only one liter is taken so that's why here we will take tris concentration is equal to number of moles that is how many weight is given here one liter of solution made from 12 .43 grams of tris which is having the molar mass 121 .135 for tris hc l that is equal to how much weight is 4 .67 is given and the molar mass is 157 .596 so the number of moles for this one is 0 .104 .33.

02:19 So the number of moles for this one is 0 .1043 m is for tris and for tris hcl it is 0 .0296 is a for tris cl the concentration so we know the concentrations pk a values that's why we will calculate ph is equal to pk a 0 .072 plus log 0 .1043 divided by 0 .0296 okay then here we will get it is 8 .072 plus it is 0 .547 then ph is equal to ph of the solution is 8 .619 okay and now we will we have another question regarding this one so same if we add hcl that is 12 m and 1m concentration hcl to tris so two trees we are adding hcl to give tris hcl okay so for this solution we have to calculate the ph value okay so here we know that the concentration of tris we know and concentration of tris hl both are having here so that's why we have moles of tris is present so we will convert them into millimoles so how many moles of this one is there so tris is tris is 0 .1043 moles are present so that is equal to 1043 millimoles it will be and the tris hcl is here it is tris hcl sorry this is tris hcl is equal to um 0 .0 296 moles so it will be 0 .0 sorry 229 .6 millimoles okay so now we have the concentration here 104 .3 millimoles and this one is multiplied by millimoles how many millimeters here 12 millimoles okay so 12 and this one is 29 .6 so when reacts completely reacts with this tris, so minus 12 and this one is also minus 12 here it is plus 12 okay then it is 90 how much 92.

05:28 3 and it is 0 and this 1 .6 millimeters of tris is present here...

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