I\'ve noticed that recently most of my chemistry questions that get answered hav

Question

I've noticed that recently most of my chemistry questions that get answered have also been incorrect. I cant help but feel like this is a discrepncy between either the methods used, or the values of the refreances when choosing Ka,Ksp,Kb, costants of the nature. In order to avoid this I will post 2 pictures. The fisrt one will be the question I am asking, and the second one will be a worked question of similar nature that I missed. I will also post the refrences that I am using. Please use the numbers off those refernces or the answer will be wrong. Thanks

asking:A solution contains 1.12×10-2 M ammonium phosphate and 1.16×10-2 M potassium hydroxide.
Solid aluminum nitrate is added slowly to this mixture.

What is the concentration of hydroxide ion when phosphate ion begins to precipitate?
[hydroxide] =  M

Missed:

Charts:

Ksp-

BromidesPbBr26.3 × 10-6

AgBr3.3 × 10-13CarbonatesBaCO38.1 × 10-9

CaCO33.8 × 10-9

CoCO38.0 × 10-13

CuCO32.5 × 10-10

FeCO33.5 × 10-11

PbCO31.5 × 10-13

MgCO34.0 × 10-5

MnCO31.8 × 10-11

NiCO36.6 × 10-9

Ag2CO38.1 × 10-12

ZnCO31.5 × 10-11ChloridesPbCl21.7 × 10-5

AgCl1.8 × 10-10ChromatesBaCrO42.0 × 10-10

CaCrO47.1 × 10-4

PbCrO41.8 × 10-14

Ag2CrO49.0 × 10-12CyanidesNi(CN)23.0 × 10-23

AgCN1.2 × 10-16

Zn(CN)28.0 × 10-12FluoridesBaF21.7 × 10-6

CaF23.9 × 10-11

PbF23.7 × 10-8

MgF26.4 × 10-9HydroxidesAgOH2.0 × 10-8

Al(OH)31.9 × 10-33

Ca(OH)27.9 × 10-6

Cr(OH)36.7 × 10-31

Co(OH)22.5 × 10-16

Cu(OH)21.6 × 10-19

Fe(OH)27.9 × 10-15

Fe(OH)36.3 × 10-38

Pb(OH)22.8 × 10-16

Mg(OH)21.5 × 10-11

Mn(OH)24.6 × 10-14

Ni(OH)22.8 × 10-16

Zn(OH)24.5 × 10-17IodidesPbI28.7 × 10-9

AgI1.5 × 10-16OxalatesBaC2O41.1 × 10-7

CaC2O42.3 × 10-9

MgC2O48.6 × 10-5PhosphatesAlPO41.3 × 10-20

Ba3(PO4)21.3 × 10-29

Ca3(PO4)21.0 × 10-25

CrPO42.4 × 10-23

Pb3(PO4)23.0 × 10-44

Ag3PO41.3 × 10-20

Zn3(PO4)29.1 × 10-33SulfatesBaSO41.1 × 10-10

CaSO42.4 × 10-5

PbSO41.8 × 10-8

Ag2SO41.7 × 10-5SulfidesCaS8 × 10-6

CoS5.9 × 10-21

CuS7.9 × 10-37

FeS4.9 × 10-18

Fe2S31.4 × 10-88

PbS3.2 × 10-28

MnS5.1 × 10-15

NiS3.0 × 10-21

Ag2S1.0 × 10-49

ZnS2.0 × 10-25SulfitesBaSO38.0 × 10-7

CaSO31.3 × 10-8

Ag2SO31.5 × 10-14

Ka&Kb-

Acetic acid

CH3COOH

1.8 × 10-5

Acetylsalicylic acid (aspirin)

HC9H7O4

3.0 × 10-4

Aluminum ion

Al(H2O)43+

1.2 × 10-5

Arsenic acid

H3AsO4

2.5 × 10-4

5.6 × 10-8

3.0 × 10-13

Ascorbic acid

H2C6H6O6

7.9 × 10-5

1.6 × 10-12

Benzoic acid

C6H5COOH

6.3 × 10-5

Carbonic acid

H2CO3

4.2 × 10-7

4.8 × 10-11

Ferric ion

Fe(H2O)63+

4.0 × 10-3

Formic acid

HCOOH

1.8 × 10-4

Hydrocyanic acid

HCN

4.0 × 10-10

Hydrofluoric acid

HF

7.2 × 10-4

Hydrogen peroxide

H2O2

2.4 × 10-12

Hydrosulfuric acid

H2S

1.0 × 10-7

1.0 × 10-19

Hypochlorous acid

HClO

3.5 × 10-8

Nitrous acid

HNO2

4.5 × 10-4

Oxalic acid

H2C2O4

5.9 × 10-2

6.4 × 10-5

Phenol

C6H5OH

1.0 × 10-10

Phosphoric acid

H3PO4

7.5 × 10-3

6.2 × 10-8

3.6 × 10-13

Sulfuric acid

H2SO4

very large

1.2 × 10-2

Sulfurous acid

H2SO3

1.7 × 10-2

6.4 × 10-8

Zinc ion

Zn(H2O)42+

2.5 × 10-10

Base

Formula

Kb

Ammonia

NH3

1.8 × 10-5

Aniline

C6H5NH2

7.4 × 10-10

Caffeine

C8H10N4O2

4.1 × 10-4

Codeine

C18H21O3N

8.9 × 10-7

Diethylamine

(C2H5)2NH

6.9 × 10-4

Dimethylamine

(CH3)2NH

5.9 × 10-4

Ethylamine

C2H5NH2

4.3 × 10-4

Hydroxylamine

NH2OH

9.1 × 10-9

Isoquinoline

C9H7N

2.5 × 10-9

Methylamine

CH3NH2

4.2 × 10-4

Morphine

C17H19O3N

7.4 × 10-7

Piperidine

C5H11N

1.3 × 10-3

Pyridine

C5H5N

1.5 × 10-9

Quinoline

C9H7N

6.3 × 10-10

Triethanolamine

C6H15O3N

5.8 × 10-7

Triethylamine

(C2H5)3N

5.2 × 10-4

Trimethylamine

(CH3)3N

6.3 × 10-5

Urea

N2H4CO

1.5 × 10-14

Acetic acid

CH3COOH

1.8 × 10-5

Acetylsalicylic acid (aspirin)

HC9H7O4

3.0 × 10-4

Aluminum ion

Al(H2O)43+

1.2 × 10-5

Arsenic acid

H3AsO4

2.5 × 10-4

5.6 × 10-8

3.0 × 10-13

Ascorbic acid

H2C6H6O6

7.9 × 10-5

1.6 × 10-12

Benzoic acid

C6H5COOH

6.3 × 10-5

Carbonic acid

H2CO3

4.2 × 10-7

4.8 × 10-11

Ferric ion

Fe(H2O)63+

4.0 × 10-3

Formic acid

HCOOH

1.8 × 10-4

Hydrocyanic acid

HCN

4.0 × 10-10

Hydrofluoric acid

HF

7.2 × 10-4

Hydrogen peroxide

H2O2

2.4 × 10-12

Hydrosulfuric acid

H2S

1.0 × 10-7

1.0 × 10-19

Hypochlorous acid

HClO

3.5 × 10-8

Nitrous acid

HNO2

4.5 × 10-4

Oxalic acid

H2C2O4

5.9 × 10-2

6.4 × 10-5

Phenol

C6H5OH

1.0 × 10-10

Phosphoric acid

H3PO4

7.5 × 10-3

6.2 × 10-8

3.6 × 10-13

Sulfuric acid

H2SO4

very large

1.2 × 10-2

Sulfurous acid

H2SO3

1.7 × 10-2

6.4 × 10-8

Zinc ion

Zn(H2O)42+

2.5 × 10-10

A solution contains 5.60x10N M sodium phosphate and g.04x10 M sodium fluoride. Solid barium acetate is added slowly to tus uurutue. What is the concentration ofphosphate ion when fluoride iou begins to precipitate? [phosphate) 5 X ME When barium acetate ia added to a Bolution of sodium phosphate and sodium fluoride two precipitates cam fom, barium phosphate and barium fuonide Notice that they have barium ion in doumon. Step 1: From the BaF2 equilibrium calculate the concentration of Ba needed to precipitate 9.04 or MofF BaF M 9.04-103 10x10 2.0s 102 MBa2 09-04x1032 Step 2: use this concentration of Ba to calculate the couceatatiou of PO left solution. Bay Poar(s) score 1.08.10 M M 12-130 012 M Step 3: compare the amommt left of PO in sohrtion 10 the initinl amommt DPO'10 5.60x10 M 1.20x10 M so BayPo precipitates until the CPO equals 1.20-10 M.

Explanation / Answer

Ksp of AlPO4 = 6.3 x 10^-19

Ksp of Al(OH)3 = 1.9 x 10^-33

So as the Ksp of Al(OH)3 is lower than that of AlPO4, Al(OH)3 would precipitate out first from the solution.

Starting from AlPO4

calculating concentration of [Al3+] when AlPO4 begins to precipitate,

[Al3+] = Ksp/[PO4^3-]

with,

[PO4^3-] = 1.12 x 10^-2 M

we get,

[Al3+] = 6.3 x 10^-19/1.12 x 10^-2 = 5.625 x 10^-17 M

Now calculating [OH-] remaining in solution when AlPO4 begins to precipitate,

[OH-] = cube rt.(Ksp/[Al3+])

          = cube rt.(1.9 x 10^-33/5.625 x 10^-17)

          = 3.24 x 10^-6 M

So,

[OH-] remining in solution when phosphate begins to precipitate = 3.24 x 10^-6 M

[*Pl. note Ksp of AlPO4 was not given above in the list provided, so it was taken from the literature. If you change this value, follow the same procedure to get the exact concentration of [OH-] remaining in solution]

Related Questions

Navigate

• Browse (All)
• Browse I
• Subjects

---

---

Integrity-first tutoring: explanations and feedback only — we do not complete graded work. Learn more.