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<p>What u have to do for this one is determine the moles of Copper sulfate is produced in a .1M of 250mL solution. moles = M X V Where M is molarity and V is volume in liters. So you do .10 (or 1/10) times 1/4L and u get 1/40. You need 1/40 moles of Copper sulfate to produce a .1M of 250ml solution. But u have to go one step further since it asks for mass. Simply multiply the molar mass by the moles and u get 6.2</p>
<p>@cadillac
Yours does. I just don’t feel like memorizing another constant (Faraday’s).</p>
<p>Thanks cadillac and everyone else, I feel quite stupid right about now. I had the moles and everything and here I was trying to do some crazy things to it.</p>
<p>ok guys… so it seems pretty certain tomorrow will be titrations… anyone wanna refresh my memory? haha</p>
<p>Ugh I’ve been studying for Physics C all weekend and haven’t done any preparation for this… lol</p>
<p>Ok for a titration, standard lab procedure is to wash the buret out with the solution with which you are titrating. Remember you have to use an indicator in whatever flask you put the other thing (acid/base) in. Common ones are phenolphthalein and methyl blue (iirc). Ok so you would swirl each time you add drop by drop of the titrant until you see the color change of the indicator stay for a longer period of time. </p>
<p>The math part of it is mainly related to a titration curve. The half equivalence point is where the pH = pKa. This is called the buffer zone and is also the half-equivalence point.
A little bit further we have the equivalence point. It is not always at 7. It is just the point where the AMOUNT of titrant is equal to the AMOUNT of what’s in the flask. One drop above this is the end point. Here, a full color change will happen (using phenolphthalein anyway).</p>
<p>Ok diprotic and triprotic acids. Those will have 2 or three “humps” on their graph indicated the ionization of each successive hydrogen. But! Know that for things like H3PO4 the first ionization is the strongest and the following two are usually much weaker.</p>
<p>How do you calculate the pH of a di/triprotic acid?</p>
<p>Do you find the concentration of H+ after the first ionization, repeat for the second and third with H2PO4 and HPO4, and add all of them together?</p>
<p>feuxfollets I think so. But the thing is it will come out to be nearly the pH of the first ionization (i.e. the first H+ coming off)</p>
<p>To further add onto Terrence’s point, you’re best to know most likely the color changes, as they’ll probably ask like “what will you see” or what indicator can you add. Bromothymol Blue goes from Blue to Yellow in the presence of CO2.</p>
<p>Not sure on phenolpthalein though.</p>
<p>hey guys! freakin out for tomm…so i took that audit test and i got a 96.5 pts…i don’t get how to find out my score. like it saye the Mc and frq are worth equally…but the mc is outta 75 pts whle the frq is outta 58…</p>
<p>Oops when I said methyl blue I meant bromothymol blue xD. Phenolpthalein will be clear in acids and hot pink in bases (they might say red)</p>
<p>Smarty you’re at a 4 or 5…and guys Im freaking out about these labs…how many questions do you think will have them?</p>
<p>phenophthalein is pink in basic solution, colorless in acidic solution.</p>
<p>@smarty99, Here is how each section is weighted:
[(MC correct) - (1/4 X Number wrong)] X 1.0667 = Weighted section I
FRQ1: (Points out of 9) x 1.7778
FRQ2: (Points out of 10) x 1.600
FRQ3: (Points out of 8) x 2.000
FRQ4: (Points out of 15) x 0.5334
FRQ5: (Points out of 8) x 1.500
FRQ6: (Points out of 8) x 1.500</p>
<p>Composite Score:
160 - 108: 5
107 - 86: 4
85 - 62: 3
61 - 43: 2
42 - 0: 1
(Source: My AP Chemistry teacher)</p>
<p>Does anyone know how to do the following question?</p>
<p>At 25 C a saturated solution of a metal hydroxide, M(OH)2, has a pH of 9.0. What is the Ksp value of the solid?</p>
<p>The answer is 5.0*10^-16</p>
<p>I think you find the pOH and then find the [OH]- , then write a ksp equation to see the relative concentration of each. In this case the ksp = (x/2) (x)^2, where x = concentration of OH-</p>
<p>pH 9 means pOH =5</p>
<p>that means the concentration of OH ions = -log [OH-] = 5 =
10^-5 Molar</p>
<p>Ksp = [M2+][OH-]^2
[M2+] = 1/2 [OH]</p>
<p>plug in values, u get 5 x 10^-16</p>
<p>Ksp =</p>
<p>-log( 10^-5 ) = X </p>
<p>ksp = (X/2)(X) ^2</p>
<p>wow thanks so much! seems like the curve is pretty sweet…can’t beleive that its actually possible to get a 5 with so many wrong!</p>
<p>That makes sense thanks.</p>