Solution Chemistry

Solutions, Problems, Solutions, Problems.

Does it ever end?

How can you express concentration?

How can you express concentration?

1) Mass % composition2) Molarity3) Molality4) Mole fraction5) Density

Mass % problems:

• Find mass %• Find amount of solute• Find total mass of solution

Mass % problems:

• Find mass %

• Mass % = mass of solute x 100 % total mass of solution

Don’t forget to add the masses of the solute and solvent for the total mass

Mass % problems:

• Find amount of solute

• Mass % = mass of solute x 100 % total mass of solution

• Multiply by total mass and divide by 100% to solve for mass of solute

Mass % problems:

• Find total mass of solution

• Mass % = mass of solute x 100 % total mass of solution

• Multiply both sides by the mass of solution first to get it out of the denominator.

Molarity problems:

• Find molarity• Find amount of solute• Find volume of solution

Molarity problems:

• Find molarity

• M= moles soluteVolume of solution (L)

Molarity problems:

• Find amount of solute

• M= moles soluteVolume of solution (L)

• Molarity x volume= moles!

Molarity problems:

• Find volume of solution

• M= moles soluteVolume of solution (L)

• Multiply both sides by the volume of solution first to get it out of the denominator.

OR!

Molarity problems:

• Find volume of solution

• Use the molarity as a conversion factor!

• moles solute x 1 L = Volume of solution! M

Dilution Problems

M x V = Moles• Moles of solute in new solution = moles in the

stock solution. Molarity goes down, volume goes up

Dilution Problems

Example:What is the concentration of a solution made by

diluting 25 ml of a .50 M HCl solution to a new volume of 150 ml?

Dilution Problems

Example:What is the concentration of a solution made by

diluting 25 ml of a .50 M HCl solution to a new volume of 150 ml?

M x V = moles..50 M x .025 L= .0125 moles HClM = mol/vol= .0125 mol / .150 L = .083 M

Dilution Problems

1) What is the concentration of a solution made by diluting 125 ml of a 2.5 M NH3 solution to a new volume of 350 ml?

2) What is the concentration of a solution made by diluting 2.5 ml of a 6.0 M NaCl solution to a new volume of 80. ml?

3) What is the concentration of a solution made by diluting 30. ml of a 1.0 M Fe(NO3)3 solution with 20. ml of water? (The final volume should be 20. + 30. = 50. ml)

Dilution Problems

Example:What volume of a 2.0 M NaOH stock solution is

required to mix 1.50 L of a .150 M NaOH solution?

Dilution Problems

Example:What volume of a 2.0 M NaOH stock solution is

required to mix 1.50 L of a .150 M NaOH solution?

M x V = moles..150 M x 1.50 L = .225 moles NaOH.225 moles NaOH x 1 L/ 2.0 moles= .113 L

Dilution Problems

1) What volume of a 6.0 M NaOH stock solution is required to mix 1.50 L of a .150 M NaOH solution?

2) What volume of a 2.0 M MgCl2 stock solution is required to mix 1.750 L of a .10 M MgCl2 solution?

3) What volume of a 1.0 M HCl stock solution is required to mix 100. ml of a .10 M HCl solution?

Volume Stoichiometry

• If you mix 10. ml of .10 M HCl with .10 M NaOH,

• …it should take 10. ml of the NaOH to react completely.

Volume Stoichiometry

• If you mix 10. ml of .10 M HCl with .20 M NaOH,

• …it should take only 5.0 ml of the NaOH to react completely.

Volume Problems

1) If you react 10.0 ml of .10 M HCl with .050 M NaOH, what volume of NaOH solution will be needed?

2) If you react 10.0 ml of .10 M H2SO4 with .050 M NaOH, what volume of NaOH solution will be needed?

3) If you react 50.0 ml of 1.0 M CaCl2 with 1.9 M Na2CO3, what volume of Na2CO3 solution will be needed?

Volume Stoichiometry

• If 10. ml of .10 M HCl reacts completely with 10. ml NaOH,

• …the concentration of the NaOH must be the same, .10 M

Volume Stoichiometry

• If 10. ml of .10 M HCl reacts completely with 20. ml NaOH,

• …the concentration of the NaOH must be half of that, .050 M.

Volume problems

• If 25.0 ml of .30 M HCl reacts completely with 25. ml NaOH, what is the concentration of the NaOH?

• If 10.0 ml of .10 M HCl reacts completely with 20. ml NaOH, what is the concentration of the NaOH?

• If 15.0 ml of .10 M HCl reacts completely with 50. ml Pb(NO3)2, what is the concentration of the Pb(NO3)2?

Acids and Bases

Examples?

• Acids• Bases

Properties of Acids and Bases• Acids • Bases

Properties of Acids and Bases• AcidsAre electrolyte solutions• Make ions in solution• Affect indicators• Have low pH• Taste sour• Neutralize basesCan cause serious burnsCorrode reactive metalsHave more H+ than OH-

(in solution)

• BasesAre electrolyte solutions• Make ions in solution• Affect indicators• Have high pH• Taste bitter• Neutralize acidsCan cause serious burnsCorrode aluminum onlyHave more OH- than H+

(in solution)

Properties of Both• AcidsAre electrolyte solutions• Make ions in solution• Affect indicators• Have low pH• Taste sour• Neutralize basesCan cause serious burnsCorrode reactive metalsHave more H+ than OH-

(in solution)

• BasesAre electrolyte solutions• Make ions in solution• Affect indicators• Have high pH• Taste bitter• Neutralize acidsCan cause serious burnsCorrode aluminum onlyHave more OH- than H+

(in solution)

BrØnsted-Lowry Definition

• Substances that donate a proton (H+ ion) in a reaction are acids.

• Substances that accept a proton (H+ ion) are bases.

Arrhenius acids and bases make H+ and OH- ions in solution. BrØnsted-Lowry bases are also Arrhenius bases.

Conjugates

• After an acid has donated a proton, the rest of the species is the conjugate base.

HAA- + H+

• After a base has accepted a proton, the resulting species is the conjugate acid.

B- + H+ HB

What is the conjugate base of…

• HCl• CH3COOH• H2SO4

• HSO4-

• H2O• NH4

+

• NH3

What is the conjugate base of…

ACID (loses H+ to form its) Conjugate base• HCl• CH3COOH• H2SO4

• HSO4-

• H2O• NH4

+

• NH3

What is the conjugate base of…

ACID (loses H+ to form its) Conjugate base• HCl ( H+ and) Cl- • CH3COOH• H2SO4

• HSO4-

• H2O• NH4

+

• NH3

What is the conjugate base of…

ACID (loses H+ to form its) Conjugate base• HCl ( H+ and) Cl- • CH3COOH( H+ and) CH3COO-

• H2SO4 ( H+ and) HSO4-

• HSO4- ( H+ and) SO4

-2

• H2O ( H+ and) OH-

• NH4+ ( H+ and) NH3

• NH3 ( H+ and) NH2-

What is the conjugate acid of…

• NO3-

• C2O4-2

• HPO4-2

• HSO4-

• H2O• F-

What is the conjugate acid of…

Base (gains H+ to form its) Conjugate acid• NO3

-

• C2O4-2

• HPO4-2

• HSO4-

• H2O• F-

What is the conjugate acid of…

Base (gains H+ to form its) Conjugate acid• NO3

- (+H+ ) HNO3

• C2O4-2

• HPO4-2

• HSO4-

• H2O• F-

What is the conjugate acid of…

Base (gains H+ to form its) Conjugate acid• NO3

- (+H+ ) HNO3

• C2O4-2 (+H+ ) HC2O4

-

• HPO4-2 (+H+ ) H2PO4

-

• HSO4- (+H+ ) H2SO4

• H2O (+H+ ) H3O+

• F- (+H+ ) HF

Nomenclature

• If the anion name then the acid name• ends in…. is…

Fill in the blanks

• HCl is _____________acid• HClO4 is _____________acid

• HClO3 is _____________acid

• HClO2 is _____________acid

• HClO is _____________acid

Fill in the blanks

• HCl is _____________acid• HClO4 is _____________acid

• HClO3 is _____________acid

• HClO2 is _____________acid

• HClO is _____________acid

Hydrogen chlorideH

ydro

gen

chlo

rate

Hydrogen perchlorate

Hydrogen hypochlorite

Hydrogen chlorite

Nomenclature

• If the anion name then the acid name• ends in…. is…• --ide Hydro___ic acid• (hypo--) --ite Hypo___ous acid• --ite ___ous acid• --ate ___ic acid• (per--) –ate Per ___ic acid

Fill in the blanks

• HNO3 is _____________acid

• HIO4 is _____________acid

• H2CO3 is _____________acid

• H3PO3 is _____________acid

• HBrO is _____________acid

Fill in the blanks

• _____________is hydrocyanic acid• _____________ is perbromic acid

• _____________ is phosphoric acid

• _____________ is sulfurous acid

• _____________ is hypoiodous acid

Show the conjugate acid/base pairs in the following reactions.

• C2O4-2+ H3O+ HC2O4

- + H2O

• CH3COOH + NH2- NH3 + CH3COO-

Show the conjugate acid/base pairs in the following reactions.

• C2O4-2+ H3O+ HC2O4

- + H2O

• CH3COOH + NH2- NH3 + CH3COO-

Acid

Base

ConjugateBase

Conjugate Acid

Show the conjugate acid/base pairs in the following reactions.

• C2O4-2+ H3O+ HC2O4

- + H2O

• CH3COOH + NH2- NH3 + CH3COO-

Acid

Acid

Base

Base

ConjugateBase

Conjugate Acid

ConjugateBase

Conjugate Acid

[H+] is inversely related to [OH-]

• When [H+] increases, [OH-] decreases in a water solution, and vice versa.

[H+] is inversely related to [OH-]

• When [H+] decreases, [OH-] increases in a water solution, and vice versa.

(Why?)

pH

• The basic (and acidic) definitions are: pH= -log [H+] [H+]= 10-pH

pOH= -log [OH-] [OH-]=10 -pOH

Kw=[H+][OH-]=1 x 10 -14 (at 25oC)

pH + pOH = 14 (at 25oC)

pH practice

• If pH is 3.38….

1) What is the pOH?

pH practice

• If pH is 3.38….

1) What is the pOH? 14-pH= 10.62

pH practice

• If pH is 3.38….

1) What is the pOH? 14-pH= 10.622) What is [H+]?

pH practice

• If pH is 3.38….

1) What is the pOH? 14-pH= 10.622) What is [H+]? 10-3.38= 4.17 x 10-4M

pH practice

• If pH is 3.38….

1) What is the pOH? 14-pH= 10.622) What is [H+]? 10-3.38= 4.17 x 10-4M3) What is [OH-]?

pH practice

• If pH is 3.38….

1) What is the pOH? 14-pH= 10.622) What is [H+]? 10-3.38= 4.17 x 10-4M3) What is [OH-]? 10-10.62=2.40x10-11M and

Kw/4.17x10-4M=2.40x10-11 M!

pH practice

• If [OH-]= 4.8 x 10-6 M…

pH practice

• If [OH-]= 4.8 x 10-6 M…

1) What is pOH?

pH practice

• If [OH-]= 4.8 x 10-6 M…

1) What is pOH? -log (4.8 x 10-6 )= 5.32

pH practice

• If [OH-]= 4.8 x 10-6 M…

1) What is pOH? -log (4.8 x 10-6 )= 5.322) What is pH?

pH practice

• If [OH-]= 4.8 x 10-6 M…

1) What is pOH? -log (4.8 x 10-6 )= 5.322) What is pH? 14-5.32= 8.68

pH practice

• If [OH-]= 4.8 x 10-6 M…

1) What is pOH? -log (4.8 x 10-6 )= 5.322) What is pH? 14-5.32= 8.683) What is [H+]?

pH practice

• If [OH-]= 4.8 x 10-6 M…

1) What is pOH? -log (4.8 x 10-6 )= 5.322) What is pH? 14-5.32= 8.683) What is [H+]? 10-8.68= 2.08 x 10-9 M and Kw/

4.8 x 10-6 = 2.08 x 10-9 M !

Please recall:

• Strong acids and bases dissociate completely in water. Weak acids/bases do not.

• Strong acids= nitric, hydrochloric, sulfuric, hydrobromic, hydroiodic, perchloric

• Strong bases-Group 1 & 2 hydroxides—(group 2’s don’t dissolve much)

Please recall:

1. What is the concentration (M) of NaOH if .35 mole NaOH is dissolved in .120 L solution?

2. What is the molarity of HCl if 12 g HCl is dissolved in .85 L of solution?

3. What is [OH-] if .35 g Ba(OH)2 is dissolved in .250 L solution?

4. What mass of H2SO4 is in 55 ml of .38 M H2SO4?

Please recall:

1. What is the concentration (M) of NaOH if .35 mole NaOH is dissolved in .120 L solution?

2. What is the molarity of HCl if 12 g HCl is dissolved in .85 L of solution?

3. What is [OH-] if .35 g Ba(OH)2 is dissolved in .250 L solution?

4. What mass of H2SO4 is in 55 ml of .38 M H2SO4?

Did you notice?

Analyze these solutionsContents pH [H+] (M) [OH-] (M) pOH Acidic

or Basic

1 .023 mol HCl /L

2 1.5g NaOH /L

3 ? mol LiOH / L

8.50

4 ? mol KOH/L

2.50

5 .? gHClO4 /L .020

6 ? mol Ba(OH)2/L

.0070

Right!Contents pH [H+] (M) [OH-] (M) pOH Acidic

or Basic

1 .023 mol HCl /L 1.64 .023 4.3x10-13 12.36 Acidic

2 1.5g NaOH /L 12.57 2.7x10-13 .0375 1.43 Basic

3 3.2 x10-6 mol LiOH / L

8.50 3.2x10-9 3.2x10-6 5.50 basic

4 3.1 x10-4 mol KOH/L

11.50 3.2x10-12 3.2x10-3 2.50 basic

5 2.0 gHClO4 /L 1.70 .020 5.0x10-13 12.30 acidic

6 .0035 mol Ba(OH)2/L

11.85 1.4x10-12 .0070 2.15 basic

Review question:

125 ml of a KOH solution is mixed so that the pH is 12.23

1) What is the pOH, [OH-] and [H+]?2) What is the [KOH] ?3) How many moles KOH was used?4) What mass of KOH was used?

(FMKOH= 56.1 g/mol)

Review question:

125 ml of a KOH solution is mixed so that the pH is 12.23

1)pOH=1.77;[OH-]=.0170M;[H+]=5.88x10-13M2) [KOH]=[OH-]= .0170M (it’s a strong base!)3)moles=MxV=.0170Mx.125L=.00213mol4) massKOH =molesKOHx FMKOH

= .00213mol x 56.1 g/mol=.119 g

Strength of acids and bases.

• HCl

• H2CO3

Strength of acids and bases.

• HCl -- strong acid

• H2CO3 -- weak acid

Strength is determined by

amount of dissociation

Strength of acids and bases.

• HCl -- strong acid, it dissociates completely

• H2CO3 -- weak acid, dissociates partly• What about their conjugates?

Strength of acids and bases.

• Cl-

• HCO3-

Strength of acids and bases.

• Cl- -- not a base

• HCO3- -- weak base

Strength is determined by

amount of association

Strength of acids and bases.

• Cl- -- not a base, it does not associate with water.

• HCO3- -- weak base, it associates partly

• What about their conjugates?

Strength of acids and bases.

The conjugate of a strong acid is not a base

The conjugate of a weak acid is a weak base

The conjugate of a strong base is not an acid

Strength of acids and bases.

The conjugate of a strong acid is not a base

The conjugate of a weak acid is a weak base the stronger the acid, the weaker the base

and vice versaThe conjugate of a strong base is not an acid