00:01
Hi, so we are to solve for the hydronium ion concentration of mandelic acid based on the given information here.
00:08
So we need to write first our ice table, mandelic acid is c8h8o3 and then we have water, this will form h3o plus and c8h7o3 minus.
00:27
So initial change equilibrium concentration, initially the concentration of the acid is 0 .20 molar and we will exclude h2o since this is in liquid phase.
00:38
So products are zero initially, this will lose some amount, this will gain, this will gain, at the equilibrium we'll have 0 .20 minus x, x and x.
00:52
So since we're calculating for the hydronium ion concentration at the equilibrium which is equivalent to x, that means we need to solve for the value of x first.
01:03
We will use the acid dissociation constant, this is equivalent to the concentration of the products, our products are hydronium and c8h7o3 over the concentration of the acid at equilibrium, sorry at equilibrium.
01:22
So let's plug in the value of ka, 4 times 10 to the negative 4, h3o plus and c8h7o3 minus is just x, you can just write x squared over 0 .20 minus x.
01:38
So rearranging this, 4 times 10 to the negative 4 multiplied by 0 .20, that's going to give us 8 times 10 to the negative 5 minus 4 times 10 to the negative 4 x and then we have here x squared.
02:05
So rearranging this to get a quadratic equation, we'll have negative x squared minus 4 times 10 to the negative 4 x plus, let's write the x outside the parenthesis, plus 8 times 10 to the negative 5.
02:26
Then we have here 0...