00:01
So, first question, how do you make 100 ml of stock solution, 1 molar tris base with a formula weight of 21 .14 gram? when you make the solution, the ph will be at about pka.
00:17
What do you need to do to bring the ph to 7 .5? so for this first question, you're making 1 molar tris base.
00:28
So the mass equals the mole times molecular weight.
00:38
Now first of all, you want to calculate the mole.
00:41
So you're making 1 molar with 100 ml stock.
00:46
So mole equals the concentration multiplied by volume.
00:53
So concentration is 1 molar and the volume is 100 ml.
01:03
So 1 molar can be converted into 1 mole per liter.
01:07
And 100 ml can be converted into 1 liter over 1000 ml.
01:18
So this is 1 mole per liter times 0 .1 liter.
01:24
So you end up having 0 .1 mole.
01:28
So from there, the mass of tris is going to be the mole, 0 .1 mole, multiplied by molecular weight, which is 121 .14 gram per mole.
01:48
So 12 .14 gram.
01:51
So this is how much tris that you need to add into the solution.
01:59
And then you add the water to all the way 100 ml solution.
02:05
So you mix 12 .14 gram of tris and water and bring the total volume to 100 ml to make the solution.
02:15
And then what do you need to bring the ph to 7 .5? so you go from 8 .06 to 7 .5.
02:28
So you will have to add hydrochloric acid.
02:36
And then you use a ph meter until the ph equals 7 .5 with constant mixing.
02:50
So that's the first question.
02:53
Let's move on to the second.
02:56
How do you make 200 ml of stock solution of 0 .25 molar of edta ph 8? and again, when stock is made, the ph is around 4.
03:10
How do you increase the ph? and then same idea, we are using the same formula right here.
03:20
So you can see that to calculate the mass of edta, you know the mole and the molecular weight.
03:26
To calculate the mole, you will need to have concentration versus and multiply by volume.
03:32
So the mole of edta is going to be the concentration, in this case, 0 .25 molar multiplied by the volume, in this case is 200 ml.
03:50
So again, 0 .25 mole per liter multiplied by 200 ml times 1 liter over 1000 ml.
04:06
So this is 0 .25 mole per liter multiplied by 0 .2 liter.
04:16
You need 0 .05 mole and the mass of edta is the mole 0 .05 multiplied by the molecular weight.
04:41
We know it's 372 .2 gram per mole.
04:48
Mole and mole cancel each other.
04:50
You need 18 .61 gram of edta.
04:55
Again, you go from ph 4 and you want to make a ph to 8 .0.
05:07
So you're going to add sodium hydroxide until the ph is stabilized at 8 .0 with constant mix.
05:22
And again, you would add 18 .61 gram of edta into a total of 200 ml of water.
05:37
So this is the final volume.
05:47
Now this third one, you want to make a buffer of tris chloride sucrose and edta to 500.
06:01
You should use the salt from quest one and two above the solid and the solid solute sucrose.
06:11
So we know we have to make a 500 ml so we can use c1 times v1 equals c2 times v2.
06:23
Now in this case, we know that c1 is initial concentration.
06:31
So tris, we know that the concentration is one molar.
06:38
And so c1 is one molar.
06:40
V1 is a none.
06:42
C2 is the final concentration.
06:44
In this case, we know this is a 10 mmol buffer, final concentration.
06:49
And v2 is the final volume.
06:51
In this case, we need 500 ml.
06:54
So now v1 easily is be 10 mmol divided by 1 molar times 500 ml.
07:04
Now 10 mmol convert into molar by multiplying 1 molar over 1000 mmol.
07:14
So then you get 0 .01 molar divided by 1 molar and multiply by 500 ml.
07:28
So you need 5 ml of stock tris.
07:38
Use the same way we use edta.
07:42
Edta start out with a stock concentration.
07:45
We made a 0 .25 molar.
07:51
And v1 is a none...