Name __________ AP Unit 9: Acids and Bases

Everything you should know already … Naming Acids: Acids are named using a unique classification system. There are 3 general guidelines:

If the anion ends in –ide … name the acid as “hydro(root)ic acid” If the anion ends in –ate … name the acid as “(root)ic acid” If the anion ends in –ite … name the acid as “(root)ous acid”

Complete the following table:

Acid Formula Anion formula Anion name Acid name

HCl Cl-1 Chloride Hydro chlor ic acid

HI I-1 Iodide Hydroiodic acid

H2SO3 SO32- Sulfite Sulfurous acid

H2Se Se2- Selenide Hydroselenic acid

HF F-1 fluoride Hydrofluoric acid

HBr Br-1 bromide Hydrobromic acid

HBrO3 BrO3-1 Bromate Bromic acid

H2SO4 SO42- Sulfate Sulfuric acid

HCN CN-1 Cyanide Hydrocyanic acid

HClO ClO-1 hypochlorite Hypochlorous acid

H2CO3 CO32- carbonate Carbonic acid

Naming Bases: Bases are named just as any other ionic compound. Name the metal first, then the name of anion. Name the following compounds:

Acid Formula Acid Name HC2H3O2 Acetic acid

LiOH Lithium hydroxide

HMnO4 Permanganic acid

Fe(OH)2 Iron(II) hydroxide

HClO4 Perchloric acid

H2Cr2O7 Dichromic acid

What kinds of compounds are acids and bases??? There are 3 general types of bonding that determine the type of label given to a particular compound/substance. These types are summarized below:

Compound/Substance Type Bonding between atoms Particle Type Ionic Compound Ionic bonds Metal Cations and Non-metal Anions

Metallic Substance Metallic bonds Metal Cations Molecular Compound Covalent bonds Molecules (non-metals only)

So where do acids belong on this table? Most acids are actually molecular compounds with covalent bonds between atoms. Like other molecules, Lewis structures can be drawn.

Try drawing Lewis structures for the simple acid molecules shown below. The rules for drawing Lewis structures have been provided for reference.

1. HF 2. HCl

3. H2S 4. H2O Analysis Questions: a. Evaluate the polarity of HF, HCl and H2S molecules.

All are polar due to differences in electronegativity of the atoms and the asymmetrical arrangement of the polar bonds. HF is most polar however, because the difference in electronegativity between H and F is the greatest.

b. Predict which molecule is more soluble in water and why. Be sure to discuss intermolecular forces in your answer. HF should be most soluble in water because it is the most polar. All of the substances are polar, so all will form dipole-dipole interactions with water molecules and be soluble. HF will form the strongest dipole-dipole forces and will therefore be the most soluble.

Now try drawing Lewis structures for more complex acids involving polyatomic ions. Normally, the hydrogen atoms attach to the oxygen atoms which surround the central atom, as shown in the example.

Example: H2SO4

5. HNO2 6. HNO3 (2 possible resonance, 1 acceptable structure) (3 possible resonance, 2 acceptable structures)

Lewis Structures: 1. Arrange atoms symmetrically and count the total number of valence electrons available for use in bonding. 2. Add single bonds between atoms. 3. Give octets to outer atoms first. 4. Extra electrons are placed on the central atom last. 5. If the central atom does not have octet, bring in lone pairs from outer atoms to make double/triple bonds.

Formal Charge: FC = VE’s – [LPE’s + ½(BE’s)] VE’s = valence electrons the atom had LPE’s = lone pair electrons around the atom BE’s = bonding electrons around the atom

7. H2CO3 8. H3PO4 (3 possible resonance, 1 acceptable structure) (no resonance, but be sure all FC’s are 0) 9. H3PO3 10. HClO3 (no resonance) (no resonance, but be sure all FC’s are 0) 11. HClO2 12. HCN (on your own) (on your own) 13. HClO 14. H2SO3 (on your own) (on your own) So where do bases belong on this table? Many bases are ionic compounds, composed of a metal cation bonded to the polyatomic ion hydroxide, OH-1.

Example: sodium hydroxide, NaOH, and zinc hydroxide, Zn(OH)2

Some bases however, are actually molecules, composed of non-metal atoms bonded covalently. Draw Lewis structures for the molecular bases shown below.

1. NH3, ammonia 2. CH3NH2, methyl amine

Arrhenius Definition of Acids and Bases: Acids and bases can be defined in many ways. The simplest definition is the Arrhenius version, which describes how an acid and/or a base will dissociate upon addition to water. For each of the following compounds, describe how it will dissociate in water according to Arrhenius AND label it as an acid or a base. HF H+ + F- Acid or base? (circle one) H2CrO4 2H+ + CrO4

-2 Acid or base? (circle one) Al(OH)3 Al+3 + 3OH-1 Acid or base? (circle one) H3PO4 3H+ + PO4

-3 Acid Chlorous acid HClO2 H+ + ClO2

- Copper(II) hydroxide Cu(OH)2 Cu+2 + 2OH-1 Hydrobromic acid HBr H+ + Br-1 H3PO3 Ni(OH)2 Properties of Acid/Base solutions: For each of the following solutions, answer the questions based on the expected solution properties. 100 mL of 3.00 M HCl solution a. What color change would be expected with the addition of phenolphthalein? No change b. If you were not following proper safety procedures and accidentally got some of this solution in your mouth, how would it taste? sour c. Would you expect this solution to conduct an electric current? yup 100 mL of 3.00 M NaOH solution a. What color change would be expected on red litmus paper dipped in the solution? blue b. What color change would be expected with the addition of phenolphthalein? pink c. If the HCl solution was added to this solution and then the pH was checked, what would the expected pH be? A neutral pH would be expected, 7 Acidity: There are many ways that a solution’s “acidity” or “alkalinity” could be evaluated, but the most common way is by analyzing the amount of H+ ions that are present in the solution. Many H+ ions = highly acidic Fewer H+ ions = less acidic (more alkaline) The amount of H+ ions in solution is kept track of using Molarity, or M, or [H+].

A solution that is termed “alkaline” contains a base, rather than an acid.

1. Solution A has an [H+] = 5.4x10-3 while Solution B has [H+]=6.7x10-13. Which solutions is more acidic? Solution A has more H+ ions, so it is more acidic. 2. Solution C has an [H+]=2x10-6 while solution D has an [H+]=3.5x10-8. Which solutions is more acidic? Solution C has more H+ ions, so it is more acidic. 3. If 500. mL of solution A is measured, how many moles of hydrogen ions are present in the solution? If 500. mL of solution B is measured, how many moles of hydrogen ions are present in the solution? Does this agree with your prediction about which is more acidic? 푴 = 풎풐풍

푳 푴 = 풎풐풍

푳

ퟓ.ퟒ풙ퟏퟎ ퟑ푴 = 풎풐풍ퟎ.ퟓ푳

ퟔ.ퟕ풙ퟏퟎ ퟏퟑ푴 = 풎풐풍ퟎ.ퟓ푳

moles = 0.0027 moles = ퟑ.ퟒ풙ퟏퟎ ퟏퟑ

4. 0.009 grams of HI is dissolved in water to produce a 750 mL solution. What is the molarity of hydrogen ions present in this solution? ퟎ.ퟎퟎퟗ품풙 ퟏ풎풐풍풆푯푰

ퟏퟐퟕ.ퟗ품풙 ퟏ풎풐풍풆푯ퟏ풎풐풍풆푯푰

= ퟕ.ퟎퟒ풙ퟏퟎ ퟓ풎풐풍풆풔푯 푴 = 풎풐풍풆풔

푳= ퟕ.ퟎퟒ풙ퟏퟎ ퟓ

ퟎ.ퟕퟓ푳= ퟗ.ퟑퟖ풙ퟏퟎ ퟓ

5. 6.6 grams of NaOH is dissolved in water to produce a 550 mL solution. What is the molarity of hydroxide present in this solution?

ퟔ.ퟔ품풙 ퟏ풎풐풍풆푵풂푶푯ퟒퟎ품

풙 ퟏ풎풐풍풆푶푯 ퟏ

ퟏ풎풐풍풆푵풂푶푯= ퟎ.ퟏퟔퟓ풎풐풍풆풔푶푯

푴 = 풎풐풍

푳= ퟎ.ퟏퟔퟓ풎풐풍풆풔

ퟎ.ퟓퟓ푳= ퟎ.ퟑ푴

pH Scale: pH is a number system that expresses the amount of hydrogen ions (or hydronium ions, depending on the definition) that are present in the solution. The pH scale will be discussed at great length in class, but here is a review of the basics. The pH formula will need to be used for some of the questions below. Label the following on the pH scale to the right. a. Acidic range b. Alkaline range c. Neutral d. Strong acid range e. Strong base range 2. If a solution has an [H+] = 1.0x10-3, what is the pH? Is it an acidic or basic solution? pH = 3 3. If a solution has an [H+] = 1.0x10-9, what is the pH? Is it an acidic or basic solution? pH = 9 4. If a solution has a pH of 7.2, what is the [H+]? ퟏퟎ ퟕ.ퟐ = ퟔ.ퟑ풙ퟏퟎ ퟖ푴

Acidic range Alkaline range

Neutral Strong Strong

5. According to the chart above, what is the approximate [H+] in orange juice? ퟏ풙ퟏퟎ ퟑ푴 6. How many times greater is the [H+] in pure water than in sea water? How does this help to explain the pH scale being a logarithmic scale? 10 times greater! On a logarithmic scale, every number is ten times greater than the previous. pOH pOH is a separate scale that is used to express the amount of hydroxide ions, OH-, present in an aqueous solution. It is found using the same formulas a pH, except with [OH-] instead of [H+]. If the formula reveals that a high concentration of hydroxide is present, the solution is less acidic and more alkaline. The opposite is true if a low concentration of hydroxide is present. Many OH- ions = highly alkaline Fewer OH- ions = less alkaline (more acidic) 1. If a solution has an [OH-] = 5.1x10-3, what is the pOH? Is it an acidic or basic solution? − 퐥퐨퐠(ퟓ.ퟏ풙ퟏퟎ ퟑ) = ퟐ.ퟐퟗ This is a basic solution because of the high OH- concentration 2. If a solution has a pOH = 8.9, what is the [OH-]? ퟏퟎ ퟖ.ퟗ =1x10-9 3. On the pOH scale below, label what range indicates an acidic solution and what range indicates a basic (alkaline) solution. Acid/Base Neutralization Reactions: If equimolar amounts of acid and base react, the two compounds are both used up (both are limiting reagants) and only a salt and water remain. This reaction usually takes the form of a double replacement reaction, following the general guideline shown below. AX + BY BX + AY H2SO4 + NaOH Na2SO4 + HOH Acid Base Salt water The equation needs to be balanced to satisfy the law of conservation of mass … 1 H2SO4 + 2 NaOH 1 Na2SO4 + 2 HOH

A simple formula is used to interconvert between [OH-] and the pOH value: pOH = -log[OH-]

Acidic range Alkaline range

Considering that most species are aqueous, and that most acids and base ionize when dissolved in water, a net ionic equation can be written…

Complete equation: 1 H2SO4 (aq) + 2 NaOH (aq) 1 Na2SO4 (aq) + 2 HOH (aq) Ionic equation: 2H+(aq) + SO4

-2(aq) + 2Na+(aq) + 2OH-(aq) 2Na+(aq) + SO4-2(aq) + 2HOH(l)

Cross off spectator ions Net ionic equation: 2H+(aq) + 2OH-(aq) 2HOH(l)

Write complete, balanced equations for each of the following acid-base neutralization reactions. 1. HCl (aq) + NaOH (aq) HOH (l) + NaCl(aq) 2. 2 HBr (aq) + Mg(OH)2 (aq) 2 HOH (l) + MgBr2 (aq) 3. H2SO4 (aq) + 2 LiOH (aq) 2 HOH (l) + Li2SO4 (aq) 4. 2 H3PO4 (aq) + 3 Ca(OH)2 (aq) 6 HOH (l) + Ca3(PO4)2 (aq) Write complete, balanced net ionic equations for each of the following. 5. HI (aq) + NaOH (aq) HOH (l) + NaI (aq) Na+ and I- are specators Net: H+ + OH- HOH 6. 2 HNO3 (aq) + Mg(OH)2 (s) 2 HOH(l) + Mg(NO3)2 (aq) NO3

- is a spectator Net: 2 H+ + Mg(OH)2 2 HOH + Mg+2 7. H2SO4 (aq) + Ca(OH)2 (s) HOH (l) + CaSO4 (s) no spectators, so that IS the net 8. H3PO3 (aq) + 3 LiOH (aq) 3 HOH (l) + Li3PO3 (aq) Li+ and PO3

-3 are spectators Net: H+ + OH- HOH

Stoichiometry with acid/base neutralization reactions: Write complete, balanced reactions before solving the following stoichiometry problems.

1. What volume of 3 M hydrochloric acid solution must be added to completely react with 100 mL of 1 M NaOH solution? HCl + NaOH HOH + NaCl 3 M 1M ? L 0.1 L 푴 = 풎풐풍풆풔

푳 ퟏ푴푵풂푶푯 = 풎풐풍풆풔푵풂푶푯

ퟎ.ퟏ푳 0.1 moles NaOH is present

ퟎ.ퟏ풎풐풍풆풔푵풂푶푯풙 ퟏ풎풐풍푯푪풍

ퟏ풎풐풍푵풂푶푯= ퟎ.ퟏ풎풐풍풆풔푯푪풍 ퟑ푴푯푪풍 = ퟎ.ퟏ풎풐풍풆풔푯푪풍

푳풊풕풆풓풔 0.033 Liters HCl

2. What volume of 6 M sulfuric acid solution must be added to completely react with 100 mL of 1 M lithium hydroxide solution? H2SO4 + 2 LiOH Li2SO4 + 2 HOH (l) 6 M 1 M ? L 0.1 L

ퟏ푴 =풎풐풍풆풔푳풊푶푯

ퟎ.ퟏ푳 = ퟎ.ퟏ풎풐풍풆풔푳풊푶푯

ퟎ.ퟏ풎풐풍풆풔푳풊푶푯풙ퟏ풎풐풍풆푯ퟐ푺푶ퟒퟐ풎풐풍풆풔푳풊푶푯 = ퟎ.ퟎퟓ풎풐풍풆풔푯ퟐ푺푶ퟒ

ퟔ푴푯ퟐ푺푶ퟒ = ퟎ.ퟎퟓ풎풐풍풆풔푯ퟐ푺푶ퟒ

푳풊풕풆풓풔 Liters = 0.00833 L of 6 M H2SO4

3. What volume of 0.05 M potassium hydroxide solution must be added to completely react with 500 mL of 0.05 M phosphoric acid solution? 3 KOH + H3PO4 K3PO4 + 3 HOH 0.05 M 0.05 M ? L 0.5 L

ퟎ.ퟎퟓ푴 =풎풐풍풆풔푯ퟑ푷푶ퟒ

ퟎ.ퟓ푳 = ퟎ.ퟎퟐퟓ풎풐풍풆풔푯ퟑ푷푶ퟒ

ퟎ.ퟎퟐퟓ풎풐풍풆풔푯ퟑ푷푶ퟒ풙ퟑ풎풐풍풆풔푲푶푯ퟏ풎풐풍풆풔푯ퟑ푷푶ퟒ = ퟎ.ퟎퟕퟓ풎풐풍풆풔푲푶푯

ퟎ.ퟎퟓ푴푲푶푯 = ퟎ.ퟎퟕퟓ풎풐풍풆풔푲푶푯

푳풊풕풆풓풔 Liters = 1.5 L of 0.05 M KOH

4. What ions are present in solution if 100 mL of 2 M hydroiodic acid solution is mixed with 300 mL of 5 M sodium hydroxide solution? HI(aq) + NaOH (aq) HOH (l) + NaI (aq) 2 M 5 M 0.1 L 0.3 L Net: H+ + OH- HOH (l) 2 M 5 M 0.1 L 0.3 L 0.2 mol 1.5 mol Find the LR: ퟎ.ퟐ풎풐풍풆풔푯풙 ퟏ풎풐풍푶푯

ퟏ풎풐풍푯= ퟏ풎풐풍풆푶푯풏풆풆풅풆풅ퟏ.ퟓ풎풐풍풆풔푶푯풂풄풕풖풂풍풍풚풑풓풆풔풆풏풕

So OH- is in excess and H+ must be the LR Since H+ is the LR, there will be none left in solution, so the only ions present are the excess OH- and the spectators which are Na+ and I-