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

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

Askiing:

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

What is the equilibrium 2- concentration when 2.85 L of a 0.125 M calcium bromide solution are mixed with 2.69Lof a 0.159 M ammonium Ca phosphate solution? [Ca2 M

Explanation / Answer

Ca+2 for

CaBr2 + (NH4)3PO4

The reaction that will occur:

Ca+2 preciptates with PO4-3

3Ca+2 + 2PO4-3 <--> Ca3(PO4)3

from your data

Ksp Ca3(PO4)3= Ca3(PO4)2 1.0 × 10-25

Ksp = 10^-25

now..

Ksp = [Ca+2]^3[PO4-3]^2

10^-25 = ([Ca+2]^3[PO4-3]^2)

we need Q

for this, we need

[Ca+2]new = M1*V1 / (V1+V2) = (0.125)(2.85)/(2.85+2.69) = 0.06430

[PO4-3]new = M2*V2 / (V1+V2) = (2.69)(0.159)/(2.85+2.69) = 0.0772

Q = ([Ca+2]^3[PO4-3]^2)

Q = (0.06430^3)(0.0772^2) = 1.584*10^-6

expect precipitation

determine limiting reactant:

3:2 ratio so

0.06430 mol of Ca+2 need --> 2/3*0.06430 = 0.04286 , we have 0.0772 M of PO4-3 so Ca+2 is limiting...

PO4-3 = (0.0772 -0.04286 ) = 0.03434 M

So..

initially

[Ca+2] = 0

[PO4-3] = 0.03434 M

in equilibrium:

[Ca+2] = 0 + 3x

[PO4-3] = 0.03434 + 2x

substitute in Ksp

10^-25 = ([Ca+2]^3[PO4-3]^2)

10^-25 =((3x)^3)(0.03434 + 2x)^2

10^-25 = 27x^3 * (0.03434 ^2 + 2*0.03434x + 4x^2)

solve for x

(10^-25) = 27x^3 * (0.0011792 + 0.06868x + 16x^2)

3.703*10^-27 = 0.0011792 x^3 + 0.06868x^4 + 16x^5

solve for x

16x^5 + 0.06868x^4+  0.0011792 x^3 + 0 x^2 + 0x - 3.703*10^-27 = 0

x = 1.46*10^-8

[ca+2] = 3x = (3)(1.46*10^-8 ) = 4.38e-8 M

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