00:01
Hi, so we are to solve for the ph of the solution here, aspirin, acetylsalicylic acid.
00:10
So let's write first a balance equation for the reaction of aspirin in water, disulfoam.
00:19
This is a weak acid, so disulfoam h3o plus and c9h7o4 minus.
00:27
Okay, that's the conjugate base.
00:29
So we will write our ice table, initial change equilibrium concentration.
00:35
Initial concentration is 0 .0117 molar and of course we will exclude h2o in our ice table.
00:41
Products are zero initially, this will lose some amount, this will gain, and this will gain.
00:46
At equilibrium we'll have 0 .0117, this will be x, next, i forgot to write minus x here.
00:53
So these are the concentrations at equilibrium and how do we solve for the value of x? we need to find the value of x so that we can solve for the ph of the solution and we will use the given acid dissociation constant, this is equivalent to the concentration of the products, over the concentration of the reactant at equilibrium.
01:17
So let's plug in the ones that we have, 3 .0 times 10 to the negative 4 is equivalent to x squared since h3o plus and c9h7o4 minus are both equivalent to x.
01:29
So we can just write x squared in the numerator and the denominator we have 0 .0117 minus x.
01:36
So rearranging this to get a quadratic equation, we'll have x minus x squared minus 3 .0 times 10 to the negative 4 x plus 3 .51 times 10 to the negative 6.
01:53
So we just equated this to zero and now we have a quadratic equation and how do we solve for the value of x? we will use quadratic formula, x is equivalent to negative v plus minus squared of v squared minus 4ac...