A CIDS AND BASES

A CID, BASE, OR NEUTRAL ? Bitter taste Doesn’t conduct electricity Feels slippery Dissolves metals Has no odor Has a strong, acrid odor Turns litmus blue Is unreactive Feels sticky Feels greasy Turns phenolphthalein solution red Dissolves grease Bubbles when baking soda is added Is oily

A RRHENIUS DEFINITION OF ACID AND BASE ACID – hydrogen containing compound that ionizes to yield hydrogen ions (H + ) in aqueous solution BASE – compound that ionizes to yield hydroxide ions (OH - ) in aqueous solution

I ONIZABLE HYDROGENS Only hydrogens in very polar bonds ionize. Some acids have more than one ionizable hydrogen DIPROTIC ACIDS 2 ionizable hydrogens (H 2 SO 4 ) TRIPROTIC ACIDS 3 ionizable hydrogens (H 3 PO 4 ) This is the hydrogen that ionizes in acetic acid Carboxyl group

A RRHENIUS BASE OR ACID ? Ca(OH) 2 HNO 3 KOH C 2 H 5 COOH HBr H 2 SO 4 Base Acid Base Acid

B RONSTED - LOWRY DEFINITION OF ACID AND BASE ACID – hydrogen ion (H + ) donor BASE – hydrogen ion (H + ) acceptor

I DENTIFY EACH REACTANT AS A HYDROGEN DONOR ( ACID ) OR HYDROGEN ACCEPTOR ( BASE ) HNO 3 + H 2 O  H 3 O + + NO 3 - CH 3 COOH + H 2 O  H 3 O + + CH 3 COO - NH 3 + H 2 O  NH OH - H 2 O + CH 3 COO -  CH 3 COOH + OH - Acid (donor) Base (acceptor) Acid (donor) Acid (donor) Acid (donor) Base (acceptor) Base (acceptor) Base (acceptor) Water acts as both a hydrogen donor and hydrogen acceptor – it acts as both an acid and a base. It is AMPHOTERIC

C ONJUGATE ACIDS & BASES CONJUGATE ACID – formed when a base gains a hydrogen ion CONJUGATE BASE – formed when an acid donates a hydrogen ion NH 3 and NH 4 + are a conjugate acid base pair

LABEL THE CONJUGATE ACID- BASE PAIRS HNO 3 + H 2 O  H 3 O + + NO 3 - CH 3 COOH + H 2 O  H 3 O + + CH 3 COO - NH 3 + H 2 O  NH OH - H 2 O + CH 3 COO -  CH 3 COOH + OH -

LEWIS ACIDS AND BASES ACID – a substance than can accept a pair of electrons to form a covalent bond BASE – a substance than can donate a pair of electrons to form a covalent bond

S ELF - IONIZATION OF WATER 2H 2 O (L) ⇆ H 3 O + (aq) + OH-(aq)  At any given time, there are only VERY small amounts of [H 3 O+] and [OH-] ions in water (1 molecule out of 550,000,000 dissociates)  Water dissociates to form equal concentrations of H 3 O+ and OH- making water neutral  At 25◦C, K w = [H+] [OH-] = [1 x ] [1 x ] = 1 x ION-PRODUCT CONSTANT OF WATER

A CIDIC SOLUTIONS VS. BASIC SOLUTIONS [H+] is greater than [OH-] [OH-] comes from self- ionization of water Extra [H+] comes from substances that dissolve in water to create [H+] [H+] is greater than 1x10 -7 Acidic SolutionBasic Solution [H+] is less than [OH-] [H+] comes from self- ionization of water Extra [OH-] comes from substances that dissolve in water to create [H+] [H+] is less than 1x10 -7 Also known as alkaline solution

I ON CONCENTRATIONS IN ACIDIC, NEUTRAL AND BASIC SOLUTIONS

A CIDIC, BASIC OR NEUTRAL ? [H+] = 6.0 x M [OH-] = 3.0 x M [H+] = 2.0 x M [OH-] = 1.0 x M [OH-][H+]= 1.0 x [H+]= 1.0 x x [H+] = 3.3 x Basic Basic (hydrogen ion concentration is less than 1.0 x Acidic (hydrogen ion concentration is greater than 1.0 x Neutral

A CIDIC SOLUTIONS VS. BASIC SOLUTIONS [H+] is greater than [OH-] [OH-] comes from self- ionization of water Extra [H+] comes from substances that dissolve in water to create [H+] [H+] is greater than 1x10 -7 pH < 7.0 pOH > 7.0 Acidic SolutionBasic Solution [H+] is less than [OH-] [H+] comes from self- ionization of water Extra [OH-] comes from substances that dissolve in water to create [H+] [H+] is less than 1x10 -7 Also known as alkaline solution pH > 7.0 pOH < 7.0

M EASURING P H Acid-Base Indicators – an acid or a base that: Dissociates in known pH range Acid and base forms are different colors in solution Accuracy challenged by changes in temp & human error pH meter Quick Accurate within.01 pH units

A CID RAIN

P H & P OH pH = –log[H+] pOH = –log[OH-] pH + pOH = 14 Use LOG key on calculator not LN to calculate pH! Use antilog (10 x ) key on calculator to calculate M from pH

S AMPLE PROBLEMS pH = -log[H+] pH = -log[8 x ] pH = Some calculators require that you push LOG key first while some require that you put in the # first then press LOG pOH = -log[OH-] pOH = -log[2 x ] pOH = 2.70 Some calculators may keep giving you errors if you try converting into – log. Just calculate using positive and switch the answer sign What is the pH of a solution if the [H+] is 8 x M? What is the pOH of a solution if the [OH-] is 2 x M?

S AMPLE PROBLEMS pOH = -log[OH-] pOH = -log[3.5 x ] pOH = 1.46 pH + pOH = – 1.46 = pH = pH M = mol solute / L solution 35 g HNO 3 / 63 g =.56 mol M =.56 mol / 5.8 L =.097 M pH = -log[H+] pH = -log[.097 ] pH = 1.01 pH + pOH = – 1.01 = = pOH What is the pH of a solution if the [OH-] is 3.5 x M? What is the pH & pOH of a solution made by adding water to 35 grams of nitric acid until the volume of the solution is 5800 mL?

P LACE THE FOLLOWING COMPOUNDS IN ORDER OF INCREASING [H+] 1M weak acid 1M strong acid 1M strong base 1M weak base 1M strong base 1M weak base 1M weak acid 1M strong acid

W RITE THE EXPRESSION FOR THE ACID DISSOCIATION CONSTANT OF THE STRONG ACID HF: K a = [H + ][A - ] [HA] K a = [H + ][F - ] [HF] HF (aq)  H + (aq) + F - (aq)

W RITE THE EXPRESSION FOR THE BASE DISSOCIATION CONSTANT FOR THE WEAK BASE HYDRAZINE. H YDRAZINE REACTS WITH WATER TO FORM N 2 H 5 + ION K b = [OH - ][ N 2 H 5 + ] [ N 2 H 4 ] N 2 H 4(aq) + H 2 O (l)  N 2 H 5 + (aq) + OH - (aq)

P LACE THE FOLLOWING ACIDS IN ORDER FROM WEAKEST TO STRONGEST ( USE TABLE ON P.607) HOOCCOOH HCO 3 - H 2 PO 4 - HCOOH HCO 3 - H 2 PO 4 - HCOOH HOOCCOOH

A.10 M SOLUTION OF FORMIC ACID HAS AN EQUILIBRIUM [ H + ] = 4.2 X M. WHAT IS THE K A OF FORMIC ACID? HCOOH (aq)  H + (aq) + HCOO - (aq) (4.2 x ) (.10 – 4.2x10 -3 ) K a = 1.8 x 10 -4