CP NT Ch 19: Acid and Bases An Intrductin Prperties f Acids 1. taste 2. Can prduce H + ( ) ins ( ) 3. Change the clr f litmus frm t 4. Reacts with such as Zn and Mg t prduce gas. Ba(s) + H 2SO 4 BaSO 4(aq) + H 2(g) 2) 5. Reacts with (CO 3 t prduce CO 2 NaHCO 3(s) + CH 3COOH(aq) NaCH 3COO(aq) + H 2O(l) + CO 2(g) 6. Acids cnduct an current Prperties f Bases 1. r caustic taste 2. A, sapy feeling 3. Can prduce OH ( ) ins 4. Ability t change litmus frm t 5. Bases an electric current 6. Bases react with acids t prduce a salt and water. This is knwn as a reactin. HCl + NaOH NaCl + H 2O HCl + Mg(OH) 2 MgCl 2 + H 2O acid base salt water Ins in Slutin slutins cntains mre hydrgen (H+) ins than hydrxide ins (OH) ph < 7 slutins cntains mre hydrxide ins (OH) than hydrgen ins ph > 7 slutins cntain an equal cncentratin f hydrgen and hydrxide ins ph = 7 Three Definitins f Acids/Bases Type Acid Base Prblems with it Arrhenius BrnstedLwry Lewis BrnstedLwry Cnjugate Acid/Base Pairs HX(aq) + H 2O(l) H 3O+(aq) + X(aq) acid base Cnjugate Cnjugate Acid Base NH 3(aq) + H 2O(l) + NH 4 (aq) + OH (aq) base acid cnjugate cnjugate acid base acid is the substance prduced when a base a hydrgen in frm an acid Cnjugate is the substance that the acid a hydrgen in t frm a base Cnjugate acidbase pair cnsists f tw substances related t each ther by dnating and accepting f a hydrgen in Practice: Cnjugate Acid and Cnjugate Base HCO 3 + H 2S H 2CO 3 + HS H 2PO 4 + OH HPO 4 2 + H 2O H 2SO 4 + NH 3 HSO 4 + NH 4 + HC 2H 3O 2 + H 2O H 3O + + C 2H 3O 2 1
Water in Acid/Base slutins Water and ther substances can act as acids and bases and are said t be. Hydrnium in = H 3O + = H + (Remember H + is a ) H 2O(l) + H 2O(l) H 3O + (aq) + OH (aq) Mnprtic and Plyprtic Acids acid dnates hydrgen in acid dnates than ne hydrgen in Strengths f Acids and Bases Electrical Cnductivity Acidic and basic slutins electricity. Strengths f Acids Acids that cmpletely inize ( ) are called strng acids. Strng acids prduce a electric current = strng HCl(aq) +H 2O(l) H 3O+(aq) + Cl(aq) acids inize in slutins = weak Prduce fewer ins and cannt cnduct electricity as efficiently as strng acids HC 2H 3O 2(aq) +H 2O(l) H 3O+(aq) + C 2H 3O 2(aq) Strength f Bases Strng bases dissciate int metal ins and ins. Weak bases inizes nly in dilute aqueus slutin Six Strng Acids Hydrchlric acid: Hydrbrmic acid: Hydridic acid: Sulfuric acid: Nitric acid: Perchlric acid: Eight Strng Bases Lithium hydrxide: Sdium hydrxide: Ptassium hydrxide: Rubidium hydrxide: Cesium hydrxide: Calcium hydrxide: Strntium hydrxide: Barium hydrxide: Acid/Base Strength vs. Cncentratin D nt get acid/base strength cnfused with. Acid/base strength is based n the ability t. Cncentratin is based n hw much is in slutin. Yu can have a strng dilute acid the acid dissciates, but there is nt much acid disslved in. Acid Inizatin Cnstant Acid cnstant ( ) is the value f the equilibrium cnstant expressin(keq) fr the inizatin f a weak acid. Ka acid Ka acid 2
Base Inizatin Cnstant The inizatin (Kb) is the value f the equilibrium cnstant expressin (Keq) fr the inizatin f a base Kb strng base Kb weak base Write the inizatin equatin and acid inizatin cnstant (Ka) expressins fr the acid HF Write the inizatin equatin and base inizatin cnstant (Kb) expressins fr the base NH 3 What is ph? H 2O(l) H + (aq) + OH (aq) Keq = Kw = The in prduct cnstant fr water (Kw) is the equilibrium cnstant (Keq) expressin fr the selfinizatin f water. The value is dependent upn temperature Kw = at 298 K Frm this yu can calculate the hydrgen in cncentratin r the hydrxide in cncentratin. At 298 K the H+ in cncentratin f an aqueus slutin is 1.0 x 10 5. What is the OH in cncentratin in the slutin? Is the slutin acidic, basic, r neutral? At 298 K the H+ in cncentratin f an aqueus slutin is 2.5 x 10 6. What is the OH in cncentratin in the slutin? Is the slutin acidic, basic, r neutral? 3
ph = The ph scale ph < 7 acidic ph = 7 neutral ph > 7 basic (alkaline) Calculating ph What is the ph f a slutin with a cncentratin f 1.0 x 10 6 hydrgen ins. What is the ph f a slutin if the cncentratin f the hydrxide ins is 9.6 x 10 4 M poh = Ammnia gas has a hydrxidein cncentratin f 4.0 x10 3 M. Calculate the poh and ph at 298 K A slutin cntains a hydrgen in cncentratin f 3.56 x 10 8 M. Calculate the ph and poh at 298 K. 4
Calculating In Cncentratin frm ph [H + ] = [OH ] = What are [H+] and [OH] in a healthy persn s bld that has a ph f 7.40? Assume that the temperature is 298 K. What are [H+] and [OH] at a ph f 2.3? What are [H+] and [OH] at a ph f 5.54? Neutralizatin Reactins A reactin in which an and a react t prduce a and A is an inic cmpund made up f a and a Example: HCl(aq) + NaOH(aq) Mg(OH) 2(aq) + HCl(aq) HNO 3(aq) + NaOH(aq) Ba(OH) 2(aq) + HCl H 2SO 4(aq) + CsOH HNO 3 + KOH 5
Titratins Purpse t find the unknwn f a slutin Prcedure add a slutin with cncentratin t a slutin f cncentratin Burette a piece f used fr dispensing accurate vlumes f a slutin the slutin f cncentratin ges in the burette Analyte (unknwn slutin) the slutin that is being Titrant (standard slutin) the slutin f cncentratin that is t the analyte Equivalence pint when the acid and base are mixed and the number f hydrgen ins the number f hydrxide ins; [H + ] = [OH ] AcidBase indicatr a chemical dye whse clrs are affected by and slutins is a cmmn acidbase indicatr End pint the pint at which the indicatr used in a titratin clr Calculatins Example 1: HC 2H 3O 2 + NaOH H 2O + NaC 2H 3O 2 In a titratin, the vlume f base needed was 9.50 ml f 0.500 M NaOH t reach the equivalence pint. The vlume f HC 2H 3O 2 was 5.89 ml. Find the mlarity f the acid. Example 2: In a titratin, 43.21 ml f a 0.03020 M RbOH slutin is required t exactly neutralize 30.00 ml f a H 2SO 4 slutin. What is the mlarity f the H 2SO 4 acid slutin? (Hint: First write the neutralizatin equatin) 6