ACIDS AND BASES

OUTCOME QUESTION(S): C12-5-07 ACID/BASE AND pH Outline acid/base theories and write acid/base equations. Include: Arrhenius, Bronsted-Lowry, Lewis. Distinguish between strong and weak acids and bases. Include: electrolytes and non-electrolytes Formulate an operational definition of pH and solve problems. Vocabulary & Concepts  Hydroxide Hydronium Amphoteric Conjugate pairs

Don’t eat stuff in the lab, please ACIDS Taste sour Burn when touching skin Turn blue litmus red Neutralize basic solutions Corrosive to metals Strong or weak electrolytes You should already be aware of most of these properties…except the taste Don’t eat stuff in the lab, please BASES Taste bitter Feel slippery Turn red litmus blue Neutralize acidic solutions Strong or weak electrolytes

Dissociates to yield aqueous hydrogen ions (H+) Bases 1. Arrhenius Definition Acids Dissociates to yield aqueous hydrogen ions (H+) Bases Dissociates to yield aqueous hydroxide ions (OH-) H+ is also called a “proton” because a Hydrogen atom without its electron IS just a proton (it has no neutrons) Svante Arrhenius (1859 - 1927)

H+ is responsible for acidic properties HCl (aq) → H+ (aq) + Cl– (aq) Remember: ionic (↓) and highly polar (↑) compounds dissociate/ionize in solution OH- is responsible for basic properties NaOH (aq) → Na+ (aq) + OH– (aq)

I guess we need I new definition for acid and base, Lowry! What about ammonia (NH3) Bronsted? It acts as a base, but doesn’t have OH-. Lowry 2. The Bronsted-Lowry Definition 20 years later: I guess we need I new definition for acid and base, Lowry! Bronsted Acids proton (H+) donor Base proton (H+) acceptor

NH3 (g) + H2O(l) NH4+(aq) + OH-(aq) Bases are proton (H+) acceptor Ammonia accepts a proton from water: H+ NH3 (g) + H2O(l) NH4+(aq) + OH-(aq) acceptor donor Hint: Follow the Hydrogen ion – who donated it, who accepted it

HCl(g) + H2O(l) H3O+(aq) H2O H+ + Cl-(aq) H3O+(aq) Acids are proton (H+) donor Hydrochloric acid donates a proton to water: H+ HCl(g) + H2O(l) H3O+(aq) H2O H+ + Cl-(aq) H3O+(aq) donor acceptor H3O+ ion called the hydronium ion H3O+ splits apart quickly, so H3O+ and H+ are written interchangeably

HCO3- + OH- CO32- + H2O HCO3- + H2O H2CO3 + OH- Amphoteric: a substance which can act as either an acid or a base depending on the situation. If you noticed…we just saw that water is amphoteric Bicarbonate ion is also amphoteric H+ HCO3- + OH- CO32- + H2O donor acceptor H+ HCO3- + H2O H2CO3 + OH- acceptor donor

B + H2O BH+ + OH- HA + H2O H3O+ + A- Conjugate acid: product of base accepting a H+. Conjugate base: product of an acid donating H+. If the compound acts as a base in the forward reaction, it will act as an acid in the reverse reaction (and vice versa) conjugate pairs B + H2O BH+ + OH- base acid Con. acid Con. base conjugate pairs These are generic equations for an acid or base reaction conjugate pairs HA + H2O H3O+ + A- acid base Con. acid Con. base conjugate pairs

NH3 (g) + H2O(l) NH4+(aq) + OH-(aq) HCO3- + OH- CO32- + H2O Label the conjugate pairs of the following reactions: conjugate pairs NH3 (g) + H2O(l) NH4+(aq) + OH-(aq) base acid Con. acid Con. base conjugate pairs conjugate pairs HCO3- + OH- CO32- + H2O acid base Con. base Con. acid conjugate pairs

Water’s electrons are attracted to BIG positive charge of Iron Problem Transition metal ions with charges of 2+ or 3+ can create an acidic solution. Step 1: Formation of a hydrate: Water’s electrons are attracted to BIG positive charge of Iron This idea is just a curiosity for us and will not be extensively covered

Step 2: Loss of H+ making acidic solution. Fe(H2O)63+ + H2O  H3O+ + Fe(H2O)5(OH)2+ H+ H All electrons are attracted inwards, so Hydrogen ion has nothing to lose and leaves

electron acceptor ● electron donor 3. Lewis Definition Acids Base electron acceptor ● electron donor H+ CH3COO-(aq) + H2O(l) OH-(aq) + CH3COOH (aq) base acid What about those metals? I think we need a broader definition? This is looking at the other “side of the coin” – bases accept H+ because they typically have electrons to donate…

CAN YOU / HAVE YOU? C12-5-07 ACID/BASE AND pH Outline acid/base theories and write acid/base equations. Include: Arrhenius, Bronsted-Lowry, Lewis. Distinguish between strong and weak acids and bases. Include: electrolytes and non-electrolytes Formulate an operational definition of pH and solve problems. Vocabulary & Concepts  Hydroxide Hydronium Amphoteric Conjugate pairs