Solution Chemistry Solutions, Problems, Solutions, Problems. Does it ever end?

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