00:01
Hello students, welcome here in this question we have a typical aspirin tablets that containing 324 nz of this one is containing estal salzlic acid which is c9 h8 o4 is given so which is a monof protic acid so k a value is given here 3 multiplied by 10 per minus 4 is k value.
00:32
So for this one, we have to calculate the ph value when four tablets of four tablets.
00:42
So four tablets means how much mass here it is multiplied by 324 m g.
00:48
That is equal to how much here 1296 m g? so that is equal to 1 .296 multiplied by 10 power minus 3.
01:00
Sorry just this much one minus this one is grams and volume is given here 320 340 ml so that is equal to 340 multiplied by in power minus 3 liters so from this number of moles we can calculate number of moles so for this sample we had to calculate the ph value and also percent dissociation also we have to calculate.
01:36
So we'll see number of moles is equal to mass is here so that is 1296 multiplied by 10 power minus divided by mass.
01:46
Molar mass of aspirin is equal to so c.
01:51
9h8 o4 molar mass is 180 grams per mole.
01:58
So here it is 180 that is equal to we will get here the mass of this one number of moles is equal to 9 .35 multiplied by 10 power minus 3 moles here.
02:17
Now we know the moles and also we know the volume.
02:22
So molarity, concentration we can calculate.
02:25
So concentration is equal to number of moals per volume.
02:29
So number of mores, 9 .3.
02:31
Multiplied by 10 power minus 3 so these are approximate values we are taking here and divided by 340 multiplied by 10 power minus 3 so these 2 will get cancelled now the molarity concentration is 2 .75 multiplied by 10 power minus 2 m is the concentration now we know the concentration so from this one we will calculate the values how so c9 h8 .4 is giving rise to dissociated to c9 h7 o4 minus plus h plus okay so here it is initially these are zero zero we can say and after at equilibrium we can take here this one is c1 minus alpha and this one is c alpha and this one is c alpha okay now the k a value is equal to c alpha multiplied by c divided by c multiplied by 1 minus alpha 1c once it gets cancelled alpha c alpha c alpha divided by 1 minus alpha so c we know that this one is equal to how much 3 multiplied by 10 power minus 4 so c alpha alpha is equal to how much here 2 .75 multiplied by 10 power minus 2 alpha square divided by 1 minus alpha.
04:01
Now the alpha squared divided by 1 minus alpha is equal to 3 .0 multiplied by 10 power minus 4 divided by 2 .75 multiplied by 10 power minus 2.
04:14
Then we will get here the way this one is equal to 1 .09 multiplied by 10 power minus 2.
04:24
Now, alpha square is equal to 1 .09 multiplied by 10 power minus 2 minus 1 .09 multiplied by 10 power minus 2 alpha.
04:42
Now, when it comes this side, alpha square plus 1 .09 multiplied by 10 power minus 2 alpha minus 1 .09 multiplied by 10 power minus 2 is equal to 0.
04:55
So we know that the formula a x squared plus b x minus c is equal to 0.
05:03
From this one, x is equal to minus b plus or minus root...