Presentation on theme: "BASES ACIDS electrolytes electrolytes sour taste bitter taste turn litmus red turn litmus blue react with metals to form H2 gas slippery feel ammonia,"— Presentation transcript:
8H2O + HNO3 H3O+ + NO3– Example (Acid) Conjugate Base Base Acid Conjugate AcidHydroniumConjugate Base
9NH3 + H2O NH4+ + OH- Example(Base) B A CA CB Hydroxide Conjugate Acid
10BOTH H2O…Acid or Base? So water is a base. So water is an acid? Amphiprotic:A chemical species that can act as EITHER, an acid or a base.
11Practice Activity HF HBr HI H3O+ Give the conjugate base for each of the following:HF HBr HI H3O+
12Practice ActivityPartner Up!Partner 1, write the following bases on the back of a cue card. (one acid per card (3 cards).Partner 2, write the conjugate acid for the acid on the other side of the card.
13Br –(aq) HSO4-(aq) CO32-(aq) HBr(aq) H2SO4(aq) HCO3-(aq) Give the conjugate acid for each of the following:Br –(aq) HSO4-(aq) CO32-(aq)HBr(aq) H2SO4(aq) HCO3-(aq)
14Practice ActivityPartner Up!Partner 1, write the following acids on the back of a cue card. (one acid per card (3 cards).Partner 2, write the conjugate base for the acid on the other side of the card.
15SO42-(aq) H2SO4(aq) HCl(aq) HCO3-(aq) HSO4-(aq) H2SO4(aq) H2CO32-(aq) Give the conjugate base for each of the following:H2SO4(aq) HCl(aq) HCO3-(aq)HSO4-(aq) H2SO4(aq) H2CO32-(aq)SO42-(aq)
17Auto-ionization of Water Most water molecules do not ionize. Only 1 in water molecules ionize! The other remain H2O!Square Brackets indicate concentrationH2O + H2O H3O+ + OH-Kw = [H3O+][OH-] = 1.0 10-14
23Mr. K’s pH/pOH Diamond of Awesome-ness Whenever you deal with pH and pOH, all you need is!.....pH/H3O+pH + pOH = 14pOH/OH-Perfect Diamond Shape-log[OH-(aq)]pH =-log[H3O+(aq)]pOH =[H3O+(aq)]=1 x 10-pH[OH-(aq)]=1 x 10-pOH=Kw[H3O+(aq)] [OH-(aq)]= 1.00 x 10-14
24-log[H3O+(aq)] pH = -log[4.7 x 10-11] -log( pH = pH = + 4.7 x 10 11 - ^-11pH =
251 x 10 ^ - 10.33 [H3O+(aq)]= 1 x 10-pH [H3O+(aq)]= 1 x 10-10.33
27Example: What is the pH of 0.050mol/L HNO3? 1 HNO3(aq) + 1 H2O(l) ↔ 1 H3O+(aq)+1NO3-(aq)C = mol/LpH =-log[H3O+(aq)]pH =-log[0.050]pH =
28Example: pH + pOH = 14 pH = 14 - pOH pH = 14 – 9.6 = 4.4 1 HBr(aq) + 1 What is the amount concentration of HBr in a solution that has a pOH of 9.6?1HBr(aq)+1H2O(l)↔1H3O+(aq)+1Br-(aq)C = ?[H3O+(aq)]=1 x 10-pH[H3O+(aq)]=1 xpH + pOH = 14[H3O+(aq)]=pH = 14 - pOHpH = 14 – 9.6=4.4
29Example: (N/G) (1/1) 1 HBr(aq) + 1 H2O(l) ↔ 1 H3O+(aq) + 1 Br-(aq) What is the amount concentration of HBr in a solution that has a pOH of 9.6?NG1HBr(aq)+1H2O(l)↔1H3O+(aq)+1Br-(aq)C = ?C =C =(N/G)(1/1)[HBr(aq)] =
30Why is the concentration of HBr the same as the hydronium ion concentration? Look at the dissociation/ionization equationHBr(aq) H +(aq) + Br -(aq)HBr(aq) + H2O(l) H30+(aq) + Br-(aq)There is a 1:1 relationship between HBr and the ions
32Substances that change colour due to the acidity of a solution. Acid – Base Indicators:
33They are a weak acid – conjugate base pair that exist in two forms (two different colours) due to presence or lack of a single proton (Hydrogen atom) in the chemical formula.
34Because of the complex nature of the chemical formula of each indicator. Abbreviations are usually used to make using indicators less complex.Ex: HLt – Lt- are the acid and conjugate base of litumus with Hlt being the red form and Lt- being the blue form
35Example Reactions Placing red litmus paper in a base: HLt(aq) + NaOH (aq) H2O (l) + Na+ (aq) + Lt- (aq)Placing blue litmus in an acid:HCl (aq) + Lt- (aq) HLt (aq) + Cl- (aq)
36Universal Indicators ***most indicators DO NOT DO THIS*** An indicator substance that changes a variety of different colours to indicate a more precise acidity of the solution being tested.***most indicators DO NOT DO THIS*****Usually only do two colours**
37Uses of Indicators pH = 2.8 – 3.2 0-4.8 2.8-8.0 7 14 0-3.2 Mark the end point of a titration (chp. 8)to estimate the pH of a solution.***We can use a series of indicators to get a fairly precise pH instead of using the more expensive pH meter.****pH = 2.8 – 3.20-4.87140-3.2Indicator Table (Pg. 10)
41Defining Acids Alternately, according to Bronsted – Lowry theory According to the modified Arrhenius theoryAcids are substances that react with water (ionize in water) to produce hydronium ions.Alternately, according to Bronsted – Lowry theoryAcids are proton donors that become basic (conjugate bases) once they donate their proton.
42Example CH3COOH(aq) + H2O(l) H3O+(aq) + CH3COO-(aq) This reaction can be explained using either definition and requires the acid react with water.H2O(l)CH3COOH(aq)H3O+(aq)CH3COO-(aq)
43Example Bronsted-Lowry Arhenius NaHSO4(aq) Na+(aq) HSO4-(aq) SO42-(aq) How can we explain using either the modified arrhenius theory or the Bronsted-Lowry theory that a solution of NaHSO4 will turn blue litmus paper red?AcidicArheniusBronsted-LowryNaHSO4(aq)Na+(aq)HSO4-(aq)SO42-(aq)HSO4-(aq)+H2O(l)→H3O+(aq)+
44Example Bronsted-Lowry Na+(aq) HSO4-(aq) SO42-(aq) HSO4-(aq) + H2O(l) How can we explain using either the modified arrhenius theory or the Bronsted-Lowry theory that a solution of NaHSO4 will turn blue litmus paper red?AcidicBronsted-LowryNa+(aq)HSO4-(aq)SO42-(aq)HSO4-(aq)+H2O(l)→H3O+(aq)+AcidConjugate Base
45BasesSo far bases have been metal hydroxides that can be explained by simple dissociation to produce hydroxide ions according to the Arrhenius theory.Ex: Ca(OH)2(aq) Ca2+(aq) + 2OH-(aq)
46Modified Arhenius Theory The original Arrhenius theory doesn’t account for the basic nature of ammonia or baking soda.The modified Arrhenius theory, that bases ionize in water (react with water) to produce hydroxide ions. Helps to explain why such substances are in fact basic.
47Example Na2CO3(s) 2Na+(aq) + CO32-(aq) Then, CO32-(aq) + H2O(l) OH-(aq) + HCO3-(aq)The Bronsted – Lowry definition of a base as a proton acceptor can also help explain this reaction.
48How did we know that the carbonate ion was going to produce a basic solution and that the sodium ion was a spectator?Bases are proton acceptors and usually have a negative charge (water and ammonia are exceptions) and acids are proton donors. Therefore, the sodium ion cannot act as an acid or a base.Na does not have H to give away and is + so it can accept an H.
49A Special CaseNonmetal oxides in water will form acidic solutions. There is a two step process to explain how this occurs.
51The overall reaction could be combined into one equation: CO2(g) + 2H2O(l) H3O+(aq) + HCO3-(aq)
52Neutralization Reactions An acid – base neutralization is a double replacement reaction that produces water (HOH) and a salt (an ionic compound)HCl(aq) + NaOH(aq) NaCl(aq) + H2O(l)
53According to the modified Arrhenius definition acids produce hydronium and bases produce hydroxide in solution. Therefore, the reaction can be written as:H3O+(aq) + OH-(aq) 2 H2O(l)Neutralization can be defined as the reaction of hydronium and hydroxide to produce water.
54How to get to that equation? The first equation is called the molecular equation. It shows everything present in a typical double replacement which you should be familiar with.HCl(aq) + NaOH(aq) NaCl(aq) + H2O(l)
55Next we need to write out the total ionic equation Next we need to write out the total ionic equation. For this equation separate all soluble compounds into ions and strong acids into hydronium and the conjugate base (anion). Insoluble compounds and weak acids will remain the same.H3O+(aq) + Cl-(aq) + Na+(aq) + OH-(aq) 2 H2O(l) + Cl-(aq) + Na+(aq)
56Now we cancel out spectator ions, ions that don’t change or react in the equation. This leaves us with the net ionic equation.H3O+(aq) + OH-(aq) 2 H2O(l)
59Strong Acids: Weak Acids: React completely (more than 99%) with water to form hydronium ions. The more hydronium ions the greater the acidic properties such as conductivity and low pH.Weak Acids:React incompletely (less than 50%) with water to form hydronium ions. Lower concentration of hydronium ions leads to less acidic properties. They have a higher pH and are poor conductors of electricity.
60Strong Bases:Soluble ionic hydroxides that dissociate 100% in water to produce hydroxide ions.Weak Bases:Reacts partially with water (less than 50%) to produce fewer hydroxide ions.
61Examples:Explain the weak base properties of baking soda (sodium bicarbonate/sodium hydrogen carbonate).Solid sodium acetate is dissolved in water. The final solution is tested and found to have a pH of about 8. Explain this evidence by writing balanced chemical equations.
62Polyprotic Substances: Polyprotic Acids:Weak acids with multiple protons to donate and whose percent reaction with water decreases after each step.Polyprotic Bases:Weak bases that can accept multiple protons and whose percent reaction with water decreases after each step.BicarbonateCaCO3