college chem?

Question

calculate the final concentrations of K+(aq), C2O4(aq), Ba2+, and Br- in a solution prepared by adding .1L of .2M K2C2O4 to .15L of .25 M BaBr2. for BaC2O4, Ksp=2.3E-8

a few drops of each of the indicators shown in the table were placed in separate portions of 1M solution of a weak acid, HX. the results are shown in the alst column of the table. what is the approximate pH of the solution containing HX? calculate the approximate value of Ka for HX.
Indicator color of HIn Color of In- pKa of HIn HX
bromphenol yellow blue 4.0 blue
blue

bromcresol yellow purple 6.0 yellow
purple

bromcresol yellow blue 4.8 green
green

alizarn yellow red 6.5 yellow

Answer 1

Final volume is V=0.1+0.15= 0.25 L
mole Ba+2= mole BaBr2 = M1V1
so at the moment of mixing you have intial Ba+2 concentration
[Ba+2]o =M1V1/ (V1+V2) = 0.25*0.15/0.25 =0.15

Similarly [C2O4(-2)]0 = M2V2/(V1+V2)= 0.2*0.1/0.25 =0.08

.. .. .. .. .. .. BaC2O4 <=> Ba+2 + C2O4(-2)
Initial .. .. .. .. .. .. .. .. .. .. .. 0.15 .. .. .. 0.08
React .. .. .. .. .. .. .. .. .. .. .. x .. .. .. .. .. x
Produce .. .. .. x
At Equil. .. .. .. .. .. .. .. .. .. 0.15-x .. 0.08-x

Ksp =[Ba+2][C2O4(-2)] = (0.15-x)*(0.08-x)= 2.3*10^-8 =>

x^2-0.23x +0.0199997= 0=>
x1= 0.15000033 rejectd because then [C2O4(-2)]<0
x2= 0.07999967

Thus [Ba+2]= 0.15 - 0.07999967= 0.07000033 =0.07 M
[C2O4(-2)]= 0.08- 0.07999967 =3.3*10^-7 M = 0.33 μM

.. .. .. .. .. HX <=> H+ +X-
Initial .. .. ..1
Dissoc. .. y
Produce .. .. .. .. .. y .. .y
At Equil .. 1-y .. .. ..y .. y

Ka=y^2/(1-y)
y=[H+]= 10^-pH

Let me re-write the table so that it is clear:

Indicator .Colour .. limit .. Colour.. Experim.
#1 .. .. .. .. yellow .. 4.0 .. .. blue .. .. blue => pH>4.0
#2 .. .. .. .. purple .. 6.0 .. .. yellow .. purple=> pH<6.0
#3 .. .. .. .. blue .. .. 4.8 .. .. green .. green => pH>4.8
#4 .. .. .. .. yellow .. 6.5 .. .. red .. .. yellow=> pH<6.5

So the pH is 4.8
for pH=4.8 Ka=(10^-(4.8*2))/(1-10^-4.8) = 2.51*10^-10
for pH=6.0 Ka =(10^-12)/(1-10^-6) =10^-12

so 10^-12 < Ka <2.51*10^-10

or if you want take the mean pH value (5.4) and find Ka for it.

Answer 2

relies upon on your considerable. I took the college, yet it particularly is for technological understanding majors (I majored in chem). My brother took intro to chem and he replace right into a business enterprise considerable. some colleges do not even have you ever are taking a lab for the intro to chem. the different one definately has a minimum of a three hour lab. additionally the gen chem has alot of math the place the different makes use of the concepts extra.