Chemical Forums
Chemistry Forums for Students => Undergraduate General Chemistry Forum => Topic started by: ziccoh on August 05, 2008, 01:25:54 PM
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1st problem
the solubility of PbCL(s) <--> Pb(ag) in water is 4.4 g/L at 25C. wgat is the value of Ksp for PbCL?.. molar mass of PbCL=278.1 g/mol..
secound question.
a formic acid buffer contains 0.50 M HCOOH and 0.50 M HCOONa is prepared before the titration (Ka HCOOH=1.8x10^-4) what will be the pH be after the addition of 10.0 M NaOH to the 100.00 buffer?
0 seconds ago - 4 days left to answer.
I missed this classes and I dont know dwhat to do... bonus questions in a HW
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the solubility of PbCL(s) <--> Pb(ag) in water is 4.4 g/L at 25C. wgat is the value of Ksp for PbCL?.. molar mass of PbCL=278.1 g/mol..
What is the "net ionic" equation and Ksp expression for the equilibrium? (do you mean PbCl2?)
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For the second question you need Henderson-Hasselbalch equation (http://www.chembuddy.com/?left=pH-calculation&right=pH-buffers-henderson-hasselbalch).
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i GOT THE ANSWER FOR THE 2 QUESTION .. I WANT SOMEONE TO DO IT SEE IF I GOT THE SAME ANSWER, FOR 1 ONE YES I MEAN PbCl2
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Show your answer and I will tell you if it is right.
You really think people who know how to calculate buffer pH are that dumb?
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I want to learn how to do this problems i just having a hard time, i always work my problems ..
for my first questions I had 2 answer the way i worked it
1.6x10^-5 and 4.0x10^-6
and for the second question i got
3.67, 3.81, 3.92 i dont know if im doing it right or not
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If you have several results, you must be doing it wrong, only one answer can be correct. Show what you did and how.
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since the forma solubility is 4.4 grams/liter then that is 4.4 grams/278.1 grams/mole = 0.01577 moles/liter of PbCL2 which means
1.58X 10^-2 moles/liter for Pb+2 and 2 X 1.58 X 10^-2 moles /liter or Cl^-2 so the Ksp = [1.58X 10^-2 ][3.16 X 10^-2]^2 = 15.78 X 10^-6
= 1.58 X10^-5
I think this is my corrct answer.. 1.6x10^-5
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im trying to use the HH equetion, but I dont think im doing it right for the second question, also im using the before and after table
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if i have MgCO3 Ksp 3.5x10^-8
and NiCO3 Ksp 1.3x10^-7
what subtance has greatest solubility in water?
if the Ksp is larger is more soluble right? thank you for yur help
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if i have MgCO3 Ksp 3.5x10^-8
and NiCO3 Ksp 1.3x10^-7
what subtance has greatest solubility in water?
if the Ksp is larger is more soluble right? thank you for yur help
For comparing the solubilty of subtances, you need to calculate its solubility, not base on Ksp. Can you show me your calculations?
Furthermore, your statement doesn't seem to be right in all cases. If 1 subtance has a larger Ksp but its solubility is smaller ( I mean the molar concentration of its constituent) can't solube better in water
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I have another question, if a chemical reaction has a AS(sys) > 0
the disorder of the system increses and the reaction is spontaneus, I know is the 2 law thermodinamics but im really confused about this...
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im trying to use the HH equetion, but I dont think im doing it right for the second question, also im using the before and after table
Usually you don't mix them in one question. Assume reaction (neutralization or protonation) went to completion, use simple stoichiometry to calculate concentration of acid and conjugated base, put into HH equation.
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I have another question, if a chemical reaction has a AS(sys) > 0
the disorder of the system increses and the reaction is spontaneus, I know is the 2 law thermodinamics but im really confused about this...
As for me, to predict whether the reaction can take place, we should base on deltaG, because it depends on dH and dS also. Hence, based on one aspect, we can't give the correct answer