Chemical Forums
Chemistry Forums for Students => Analytical Chemistry Forum => Topic started by: bblue on May 30, 2009, 03:00:53 PM
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Rank the following five salts in order of decreasing solubility, in terms of mass per unit volume.
(The most soluble gets rank 1, the least soluble gets rank 5.)
Ag3PO4 (Ksp = 1.80×10-18)
Ag2CrO4 (Ksp = 9.00×10-12)
Ca5(PO4)3F (Ksp = 1.00×10-60)
Ca3(PO4)2 (Ksp = 1.30×10-32)
AgCl (Ksp = 1.60×10-10)
So here is my work:
i first found the concentration of the ions:
Ag3PO4 : 1.60685E-5 M
Ag2CrO4 : 1.31037E-4 M
Ca5(PO4)3F : 6.109086E-8 M
Ca3(PO4)2 : 1.644765E-7 M
AgCl : 1.264911E-5 M
Then i used the concentrations and multiplied it by the molar mass and got the following solubilities [g / L]
Ag3PO4 : .0067259 g/L
Ag2CrO4 : .0434687 g/L
Ca5(PO4)3F : 3.0808E-5 g/L
Ca3(PO4)2 : 5.10167E-5 g/L
AgCl : .0081288 g/L
So the salt with the highest solubility would be the salt with the highest number:
3) Ag3PO4
1) Ag2CrO4
5) Ca5(PO4)3F
4) Ca3(PO4)2
2) AgCl
The rank that i have shown is incorrect ???
and i dont know why
can someone PLEASE check my work
THANK YOU!!
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i first found the concentration of the ions:
Ag3PO4 : 1.60685E-5 M
Ag2CrO4 : 1.31037E-4 M
Ca5(PO4)3F : 6.109086E-8 M
Ca3(PO4)2 : 1.644765E-7 M
AgCl : 1.264911E-5 M
Which ions?
How they are related to the concentration of the salt?
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well for the Ag3PO4 salt, this is how i found the concentration:
ksp = [3*x]^3 *
1.80×10-18 = 27(x^4)
x = 1.6E-5 M
x = [PO4]
and it would also equal to the concentration of the salt
wouldn't it?
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So far so good. Show how you have dealt with Ca3(PO4)2.
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ok well here is my work for Ca3(PO4)2:
1.30E-32 = [3x]^3*[2x]^2
= 108(x^5)
x = 1.644765E-7 M
1.644765E-7 M * 310.17672 g = 5.10167E-5 g/L
is my work right?
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No.
How many moles of Ca2+ per one mole of Ca3(PO4)2?
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wouldn't there be 3 moles for every 1 mole of Ca3(PO4)2??
Ca3(PO4)2 :rarrow: 3 Ca2+ + 2 PO42-
or is this eqn wrong, would Ca2+ actually exist as Ca22+ b/c the charges aren't really making any sense to me
I dont know how they got the 3 on the left side for the Ca
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PO43-
Yes, 3 moles of Ca2+ per mole of Ca3(PO4)2. Now, if so - what is concentration of Ca3(PO4)2 for a given concentration of Ca2+?
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i THINK i understand what you are trying to say...
so the concentration i found is actually 3 times more than the concentration of my salt right?
but would i have to divide by 2 or would i have to divide by 3 ??
and what exactly did i find the concentration of ??
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Argh, sorry - my mistake. You wrote
i first found the concentration of the ions:
and I was sure you did a classic mistake of not converting between ions/salt concentration, but your x was all the time salt concentration and your approach was correct.
Problem seems to be much simpler. Check your math for AgCl.
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i did the problem again and i got the same results...
AgCl :rarrow: Cl- + Ag+
1.60E-10 =
1.60E-10 = x^2
x = 1.264911E-5 M
1.264911E-5 M * 143.321 g = .008128832 g/L
is there anything else that could be wrong with my calculations?
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1.264911E-5 M * 143.321 g = .008128832 g/L
Check it again.
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Rank the following five salts in order of decreasing solubility, in terms of mass per unit volume.
(The most soluble gets rank 1, the least soluble gets rank 5.)
Ag3PO4 (Ksp = 1.80×10-18)
Ag2CrO4 (Ksp = 9.00×10-12)
Ca5(PO4)3F (Ksp = 1.00×10-60)
Ca3(PO4)2 (Ksp = 1.30×10-32)
AgCl (Ksp = 1.60×10-10)
So here is my work:
i first found the concentration of the ions:
Ag3PO4 : 1.60685E-5 M
Ag2CrO4 : 1.31037E-4 M
Ca5(PO4)3F : 6.109086E-8 M
Ca3(PO4)2 : 1.644765E-7 M
AgCl : 1.264911E-5 M
Then i used the concentrations and multiplied it by the molar mass and got the following solubilities [g / L]
Ag3PO4 : .0067259 g/L
Ag2CrO4 : .0434687 g/L
Ca5(PO4)3F : 3.0808E-5 g/L
Ca3(PO4)2 : 5.10167E-5 g/L
AgCl : .0081288 g/L
So the salt with the highest solubility would be the salt with the highest number:
3) Ag3PO4
1) Ag2CrO4
5) Ca5(PO4)3F
4) Ca3(PO4)2
2) AgCl
The rank that i have shown is incorrect ???
and i dont know why
can someone PLEASE check my work
THANK YOU!!
hello....I'm a new member here!nice to meet you all!
i think the ranking is suppose like this :-
3) Ag3PO4
2) Ag2CrO4
5) Ca5(PO4)3F
4) Ca3(PO4)2
1) AgCl
is this the correct answer?
i think if we are trying to arrange the solubility of few salts,we should just compare the Ksp of the salts only,we are not suppose to calculate the concentration of each ion which exists in the salt.So,i think those equation is not necessary..
anyway,that's my opinion on the question.....i hope i can help someone there by reply this post! :)
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i think if we are trying to arrange the solubility of few salts,we should just compare the Ksp of the salts only
Salt XY has solubility 0.01M - what is its Ksp?
Salt X2Y3 has 5 times higher solubility of 0.05M - what is its Ksp?
If you compare Ksp of both salts, will you get result telling you that second salt has greater solubility?
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i think if we are trying to arrange the solubility of few salts,we should just compare the Ksp of the salts only
Salt XY has solubility 0.01M - what is its Ksp?
Salt X2Y3 has 5 times higher solubility of 0.05M - what is its Ksp?
If you compare Ksp of both salts, will you get result telling you that second salt has greater solubility?
i already calculate the question you give me....OK below is my answer for your question :-
the Ksp for salt XY is [0.01][0.01]=0.0001M-2
the Ksp for salt X2Y3 is [2(0.05)]2[3(0.05)]3=0.00003375M-5
so,in the end the Ksp of salt XY is higher than Ksp for salt X2Y3 then i can know that salt XY is more soluble than salt X2Y3.
Am i right?
thanks for solving my misunderstanding during i learning this topic.....thank you again!now i know my mistake! ;D
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so,in the end the Ksp of salt XY is higher than Ksp for salt X2Y3 then i can know that salt XY is more soluble than salt X2Y3.
If by "i can know that salt XY is more soluble than salt X2Y3" you mean "I will get to the wrong conclusion that salt XY is more soluble than salt X2Y3" - you are right.
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so,in the end the Ksp of salt XY is higher than Ksp for salt X2Y3 then i can know that salt XY is more soluble than salt X2Y3.
If by "i can know that salt XY is more soluble than salt X2Y3" you mean "I will get to the wrong conclusion that salt XY is more soluble than salt X2Y3" - you are right.
maybe my English is too weak.....i can't get what you trying to tell me...about the question you give....am i giving the correct answer?
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Rank the following five salts in order of decreasing solubility, in terms of mass per unit volume.
(The most soluble gets rank 1, the least soluble gets rank 5.)
Ag3PO4 (Ksp = 1.80×10-18)
Ag2CrO4 (Ksp = 9.00×10-12)
Ca5(PO4)3F (Ksp = 1.00×10-60)
Ca3(PO4)2 (Ksp = 1.30×10-32)
AgCl (Ksp = 1.60×10-10)
So here is my work:
i first found the concentration of the ions:
Ag3PO4 : 1.60685E-5 M
Ag2CrO4 : 1.31037E-4 M
Ca5(PO4)3F : 6.109086E-8 M
Ca3(PO4)2 : 1.644765E-7 M
AgCl : 1.264911E-5 M
Then i used the concentrations and multiplied it by the molar mass and got the following solubilities [g / L]
Ag3PO4 : .0067259 g/L
Ag2CrO4 : .0434687 g/L
Ca5(PO4)3F : 3.0808E-5 g/L
Ca3(PO4)2 : 5.10167E-5 g/L
AgCl : .0081288 g/L
So the salt with the highest solubility would be the salt with the highest number:
3) Ag3PO4
1) Ag2CrO4
5) Ca5(PO4)3F
4) Ca3(PO4)2
2) AgCl
The rank that i have shown is incorrect ???
and i dont know why
can someone PLEASE check my work
THANK YOU!!
ya.....i know the answer already...
the calculation of AgCl really has problem with it!
the answer for this question is actually like this:
2) Ag3PO4
1) Ag2CrO4
5) Ca5(PO4)3F
4) Ca3(PO4)2
3) AgCl(0.001813g/L)
am i right? :)