The Acid Test Acids, Bases and pH

Range of pH scale The pH scale ranges from 0 to 14. There are no units of measure for pH *

What do the numbers mean?  A pH of 7 is neutral  Pure water has a pH of 7*

How about below 7? Anything below 7 is acidic 0 is the most acidic and is the least acidic The further something is from 7 the more acidic it is*

How about above 7?  higher than 7 is basic/alkaline  So is a weak base and 14 is the most basic (or alkaline)*

pH Range Neutral [H + ] > [OH - ] [H + ] = [OH - ] [OH - ] > [H + ] Acidic Basic

The pH Scale  pH measures acidity and alkalinity (how basic) a liquid is*

Ionization of Water Occasionally, in water, a H + is transferred between H 2 O molecules H : O : + : O : H H : O : H + + : O : H H H H water molecules hydronium hydroxide ion (+) ion (-)

Measuring pH Litmus paper, pH paper, and pH meters*

Litmus paper Litmus paper cannot tell you the exact pH of a substance. It can only tell you if it is an acid or a base Blue litmus turns pink in the presence of an acid Red litmus turns blue in the presence of a base*

pH paper pH paper can tell you approximate pH values. By placing one end of the pH paper in the solution it will turn a color which can be matched to the color code key. *

Indicators Indicators: Weak organic acids and bases whose colors differ from the colors of their conjugate acids or bases. The color is best viewed from above against a white background

Table of Indicators Acid / Base Indicators IndicatorLower ColorpH RangeUpper Color methyl violetyellow-green violet methyl orangered yellow congo redblue red bromocresol greenyellow blue methyl redred yellow bromocresol purpleyellow-green violet bromothymol blueyellow blue phenol redyellow red-violet cresol redyellow violet phenolphthaleincolorless dark pink Phenolphthalein is a common indicator to use in neutralization titrations. The solution is considered neutral when the solution holds a very faint pink color for half a minute or more. alizarin yellow Ryellow dark orange

pH Meter  The most precise and usually more accurate way to measure pH is using a pH meter which directly measures the amount of [H 3 O + ] in the solution  Uses an electrode which specifically measures the pH of the solution.  This is a larger model. Some are small enough to be hand-held.*

What is an Acid? Sour Taste (We never taste chemicals in lab) release hydrogen (H + ) React with metals to release H 2 React with a base to produce water and a salt (neutralization reaction) Some that completely dissociate conduct current (electrolytes) Turns blue litmus paper red*

Naming Acids Binary (begin with hydro-) Oxyacids do not have hydro- *

Naming Binary Acids Binary acids contain hydrogen and one other element Binary acids begin with hydro- Binary acids end with –ic*

Test your naming skills of these acids HF HCl HBr HI H 2 S Hydrofluoric acid Hydrochloric acid Hydrobromic acid Hydroiodic acid Hydrosulfuric acid*

Oxyacid An acid that is a compound of hydrogen, oxygen and a third element (usually a nonmetal) These do not contain hydro- Can end in either –ic or –ous*

Name these Oxyacids CH 3 COOH H 2 CO 3 HIO 3 HClO HClO 2 HClO 3 HClO 4 HNO 2 Acetic acid Carbonic acid Iodic acid Hypochlorous acid Chlorous acid Chloric acid Perchloric acid Nitrous acid*

Name these oxyacids HNO 3 H 3 PO 4 H 3 PO 3 H 2 SO 4 H 2 SO 3 Nitric acid Phosphoric acid Phosphorous acid Sulfuric acid Sulfurous acid*

Common Industrial Acids Sulfuric Nitric Phosphoric Hydrochloric Acetic *

Sulfuric Most commonly produced acid worldwide Petroleum refining Metallurgy Fertilizer manufacturing Production of metal, paper, paint, dyes, detergents Automobile batteries*

Sulfuric Acid Can be used to dehydrate (water removing) Sugar can be dehydrated by this acid Has the same effect on organic tissue causing severe burns *

Nitric Acid Volatile and unstable in its pure form Rarely used in its pure form Stains yellow and burns skin Used in the making of explosives rubber, plastics, dyes and pharmaceuticals *

Phosphoric Acid Manufacture of fertilizer and animal feed Flavoring agent in dilute form Cleaning agent for dairy equipment Manufacture of detergents and ceramics*

Hydrochloric acid Produced in your stomach to aid in digestion Used to remove surface impurities of metals (iron and steel) Cleaning agent in food industry Also known as muriatic acid in a dilute form Adjust the pH of Swimming pools*

Different Definitions of Acids and Bases Arrhenius Bronsted-Lowry Lewis*

Arrhenius Acids and Bases Arrhenius acid is a chemical compound that increased the concentration of H + in an aqueous solution Arrhenius base is a chemical that increases the concentration of OH - ions in an aqueous solution *

Characteristics of Acids and Bases Acids Taste sour Donate a H + pH less than 7 Turn litmus paper red Turn bromothymol blue to yellow Turn phenolphthalein colorless Neutralize bases Bases Taste bitter Usually ends in -OH pH greater than 7 Turn litmus paper blue Turn bromothymol blue to blue Turn phenolphthalein pink Feel slippery to touch Neutralize acids*

Learning Check AB1 Describe the solution in each of the following as: 1) acid 2) base or 3)neutral. A. ___soda B. ___soap C. ___coffee D. ___ wine E. ___ water F. ___ grapefruit*

Solution AB1 Describe each solution as: 1) acid 2) base or 3) neutral. A. _1_ soda B. _2_ soap C. _1_ coffee D. _1_ wine E. _3_ water F. _1_ grapefruit*

Learning Check AB2 Identify each as characteristic of an A) acid or B) base ____ 1. Sour taste ____ 2. Produces OH - in aqueous solutions ____ 3. Chalky taste ____ 4. Is an electrolyte ____ 5. Produces H + in aqueous solutions*

Solution AB2 Identify each as a characteristic of an A) acid or B) base _A_ 1. Sour taste _B_ 2. Produces OH - in aqueous solutions _B_ 3. Chalky taste A, B 4. Is an electrolyte _A_ 5. Produces H + in aqueous solutions*

Arrhenius Acids and Bases Acids produce H + in aqueous solutions water HCl H + (aq) + Cl - (aq) Bases produce OH - in aqueous solutions water NaOH Na + (aq) + OH - (aq)*

Learning Check AB3 Give the names of the following A. HBr (aq)1. bromic acid 2. bromous acid 3. hydrobromic acid B. H 2 CO 3 1. carbonic acid 2. hydrocarbonic acid 3. carbonous acid*

Solution AB3 A. HBr3. hydrobromic acid The name of a nonoxy acid begins with the prefix hydro- and ends with -ic acid. In a nonoxy acid, the negative anion end in -ide. B. H 2 CO 3 1. carbonic acid The name of an oxyacid is named with the stem of the anion (carbonate) changed to -ic acid *

Some Common Bases NaOHsodium hydroxide KOH potassium hydroxide Ba(OH) 2 ________________________ Mg(OH) 2 ________________________ Al(OH) 3 aluminum hydroxide*

Learning Check AB4 Match the formulas with the names: A. ___ HNO 2 1) hydrochloric acid B. ___Ca(OH) 2 2) sulfuric acid C. ___H 2 SO 4 3) sodium hydroxide D. ___HCl4) nitrous acid E. ___NaOH5) calcium hydroxide*

Solution AB4 Match the formulas with the names: A. _4__ HNO 2 1) hydrochloric acid B. _5__Ca(OH) 2 2) sulfuric acid C. _2__H 2 SO 4 3) sodium hydroxide D. _1__HCl4) nitrous acid E. _3__NaOH5) calcium hydroxide*

Learning Check AB5 Acid, Base Name or Salt CaCl 2 _______________________ KOH_______________________ Ba(OH) 2 ______ _________________ HBr_______________________ H 2 SO 4* ________________________

Solution AB5 Acid, Base Name or Salt CaCl 2 saltcalcium chloride KOHbasepotassiuim hydroxide Ba(OH) 2 basebarium hydroxide HBracidhydrobromic acid H 2 SO 4 acidsulfuric acid*

Bronsted-Lowry Acids Acids are hydrogen ion (H +) donors Bases are hydrogen ion (H + ) acceptors HCl + H 2 O H 3 O + + Cl - donor acceptor + - +

Strengths of Acids and Bases Strong acids completely ionize (100%) in aqueous solutions HCl + H 2 O H 3 O + + Cl - (100 % ions ) Strong bases completely (100%) dissociate into ions in aqueous solutions. NaOH Na + (aq) + OH - (aq) (100 % ions)*

NH 3, A Bronsted-Lowry Base When NH 3 reacts with water, most of the reactants remain dissolved as molecules, but a few NH 3 reacts with water to form NH 4 + and hydroxide ion. NH 3 + H 2 O NH 4 + (aq) + OH - (aq) acceptor donor+

Strong and Weak Acids and Bases Strong acids HCl, HNO 3, H 2 SO 4 Most other acids are weak. Strong bases NaOH, KOH, and Ca(OH) 2 Most other bases are weak.*

Learning Check SW1 Identify each of the following as a 1) strong acid or base 2) weak acid 3) weak base A. ___ HCl (aq) B. ___ NH 3 (aq) C. ___ NaOH (aq) D. ___ H 2 CO 3 (aq)

Solution SW1 Identify each of the following as a 1) strong acid or base 2) weak acid 3) weak base A. _1__ HCl (aq) B. _3__ NH 3 (aq) C. _1__ NaOH (aq) D. _2__ H 2 CO 3 (aq)*

Antacids Used to neutralize stomach acid (HCl) Many contain one or more weak bases Alka-Seltzer: NaHCO 3, citric acid, and aspirin Di-gel: CaCO 3 and Mg(OH) 2 Gelusil: Al(OH) 3 and Mg(OH) 2 Maalox: Al(OH) 3 and Mg(OH) 2 Mylanta: Al(OH) 3 and Mg(OH) 2*

More Antacids Milk of Magnesia: Mg(OH) 2 Rolaids: AlNa(OH) 2 CO 3 aluminum sodium dihydroxy carbonate Tums: CaCO 3 Tempo: CaCO 3, Al(OH) 3, Mg(OH) 2*

Types of Acids Monoprotic Diprotic Polyprotic *

Monoprotic An acid that donates one proton HCl CH 3 COOH (the H on the end is donated)*

Diprotic Donates two protons Ex. H 2 SO 4*

Polyprotic Donates more than two hydrogen atoms Ex. H 3 PO 4*

Lewis Acids and Bases Lewis Acid: atom, ion, or molecule that accepts an electron pair to form a covalent bond Lewis Base: atom, ion, or molecule that donates an electron pair to form a covalent bond *

Concentrations In lab, our concentrations are marked like this 0.01 M M = concentration of moles per liter The bigger the number the higher the concentration. Which one is a stronger concentration? M or 0.1M? *

Dilutions Add water Volume increases. New concentration is less than initial*

Concentration of A Diluted Solution A 25 mL sample of a 6.0 M KOH is diluted by adding 75 mL of water. Calculate the new concentration of the KOH solution. Moles KOH = L x 6.0 moles = 0.15 moles 1 L New volume = 25 mL + 75 mL = 100. mL = L New molarity = 0.15 moles = 1.5 M* L

Learning Check SW 2 A 125 mL sample of a 3.0 M HCl is diluted by adding 250 mL of water. The new concentration of the HCl solution is 1) 8.0 M 2) 1.5 M 3) 1.0 M*

Solution SW 2 3) 1.0 M moles HCl = L x 3.0 moles = mole 1 L new M = mole1.0 M HCl L (new volume)*

Learning Check SW 3 A 50.0 mL sample of 15% sucrose solution is diluted by adding 200. mL of water. The new concentration of the sucrose solution is 1) 3.0 % 2) 7.5 % 3) 10. %*

Learning Check SW 3 A 50.0 mL sample of 15% sucrose solution is diluted by adding 200. mL of water. The new concentration of the sucrose solution is 1) 3.0 % g sucrose = 50.0 mL x 15 g sucrose = 7.5 g 100 mL new % = 7.5 g sucrose = 3.0 % sucrose 250 mL (new volume) *

Neutralization Reactions When acid and bases with equal amounts of hydrogen ion H + and hydroxide ions OH - are mixed, the resulting solution is neutral. NaOH (aq) + HCl(aq) NaCl + H 2 O base acid salt water Ca(OH) HCl CaCl 2 + 2H 2 O base acid salt water*

Neutralization H 3 O + and OH - combine to produce water H 3 O + + OH -  2 H 2 O from acid from base neutral Net ionic equation: H + + OH -  H 2 O*

Ionic Equations for Neutralization Write strong acids, bases, and salt as ions H + + Cl - + Na + + OH - Na + + Cl - + H 2 O Cross out matched ions H + + Cl - + Na + + OH - Na + + Cl - + H 2 O Write a net ionic reaction H + + OH - H 2 O*

Balancing Neutralization Equations Write the equation for the neutralization between magnesium hydroxide and nitric acid. 1. Write the formulas of the acid and base Mg(OH) 2 + HNO 3 2. Balance to give equal OH - and H + Mg(OH) HNO 3*

3. Write the products: Mg(OH) 2 + 2HNO 3 Mg(NO 3 ) 2 + H 2 O saltwater (metal and nonmetal ) 4. Balance products Mg(OH) HNO 3 Mg(NO 3 ) H 2 O*

Learning Check N2 Select the correct group of coefficients for the following neutralization equations A. __ HCl + __ Al(OH) 3 __AlCl 3 + __ H 2 O 1) 1, 3, 3, 12) 3, 1, 1, 1 3) 3, 1, 1 3 B.__ Ba(OH) 2 + __H 3 PO 4 __Ba 3 (PO 4 ) 2 + __ H 2 O 1) 3, 2, 2, 22) 3, 3, 1, 6 3) 2, 3, 1, 6

Solution N2 A. 3HCl + 1Al(OH) 3 1AlCl 3 + 3H 2 O B. 3Ba(OH) 2 + 2H 3 PO 4 1Ba 3 (PO 4 ) 2 + 6H 2 O*

Learning Check N3 Write a balanced equation and calculate the mL of 2.00 M H 2 SO 4 required to neutralize 50.0 mL of 1.00 M KOH? ___H 2 SO 4 + ___KOH ___K 2 SO 4 + H 2 O 1)12.5 mL 2) 50.0 mL3) 200. mL*

Solution N3 How many mL of 2.00 M H 2 SO 4 are required to neutralize 50.0 mL of 1.00 M KOH? H 2 SO 4 + 2KOH K 2 SO 4 + 2H 2 O L x 1.00 mole KOH x 1 mole H 2 SO 4 x 1 L 2 mole KOH 1 L x 1000 mL = 12.5 mL 2 mole KOH 1 L *

Learning Check N4 A 25 mL sample of phosphoric acid is neutralized by 40. mL of 1.5 M NaOH. What is the molarity of the phosphoric acid solution? 3NaOH + H 3 PO 4 Na 3 PO 4 + 3H 2 O 1) 0.45 M2) 0.80 M3) 7.2 M*

Solution S L x 1.5 mole NaOH x 1 mole H 3 PO 4 1 L 3 mole NaOH x 1 = 0.80 mol/L = 0.80 M* L ***

Logarithms and pH Calculations Scientific Notation Review Log Review (or Introduction) pH formulas pH calculations

Pure Water is Neutral Pure water contains small, but equal amounts of ions: H 3 O + and OH - H 2 O + H 2 O H 3 O + + OH - hydronium hydroxide ion ion 1 x M 1 x M* H3O+H3O+ OH -

Acids Increase H + HCl (g) + H 2 O (l) H 3 O + (aq) + Cl - (aq) More [H 3 O + ] than water > 1 x M As H 3 O + increases, OH - decreases [H 3 O + ] > [OH - ]* H3O+H3O+ OH -

Bases Increase the hydroxide ions (OH - ) H 2 O NaOH (s) Na + (aq) + OH - (aq) More [OH - ] than water, [OH - ] > 1 x M When OH - increases, H 3 O + decreases [OH  ] > [H 3 O + ]* H3O+H3O+ OH -

Using logarithms and scientific notation Logarithms also called logs are exponents Log of (1 x ) = -14 Log of = 1 x = -3 You can also take the –log which would be –log = -log 1 x = -(-5) = 5*

Using the Calculator 1.0 x x Enter 1.0 EE +/- 14  4.0 EE +/- 5 = 2.5 x 10 –10*

pH Indicates the acidity [H 3 O + ] of the solution pH = - log [H 3 O + ] From the French pouvoir hydrogene (“hydrogen power” or power of hydrogen)*

In the expression for [H 3 O + ] 1 x 10 -exponent the exponent = pH [H 3 O + ] = 1 x 10 -pH M* pH

Calculating pH pH is found by using the formula pH = - log [H 3 O + ] pH + pOH = 14 pOH = -log [OH - ]*

pH on the Calculator [H 3 O + ] is 4.5 x M pH = 4.5 x EXP(or EE) 6+/- LOG +/- = 5.35*

Applying logs to pH calculations If you have an acid with concentration of 0.01M what is the pH? Answer: 0.01 = 1x10 -2 pH = -log (1x10 -2 ) = -(-2) = 2*

Some [H 3 O + ] and pH [H 3 O + ] pH 1 x M 5 1 x M 9 1 x M 11*

Applying concentration to base pH If you have a BASE with concentration of M what is the pH? = 1 x pOH = -log (1x10 -4 ) =-(-4) = 4 but this is pOH, so then we have to say pH + pOH = 14. So pH + 4 = 14; thus, pH = 10.*

Learning Check pH4 A. The [H 3 O + ] of tomato juice is 1 x M. What is the pH of the solution? 1) - 42)43)8 B. The [OH - ] of an ammonia solution is 1 x M. What is the pH of the solution? 1) 32)113)-11*

Solution pH4 A. pH = - log [ 1 x ] = -(- 4) = 4 B. [H 3 O + ] = 1 x pH = - log [ 1 x ] = -(- 11) = 11*

Learning Check pH5 The pH of a soap is 10. What is the [H 3 O + ] of the soap solution? 1) 1 x M 2) 1 x M 3) 1 x M*

Solution pH5 The pH of a soap is 10. What is the [H 3 O + ] of the soap solution? [H 3 O + ] = 1 x 10 -pH M = 1 x M*

Learning Check pH6 A soap solution has a [H 3 O + ] = 2 x M. What is the pH of the solution? 1)8 2) 7.7 3)6*

Solution pH6 A soap solution has a [H 3 O + ] = 2.0 x M. What is the pH of the solution? B) 2.0 EE 8 +/- LOG +/- = 7.7*

Learning Check pH7 Identify each solution as 1. acidic 2. basic3. neutral A. _____ HCl with a pH = 1.5 B. _____ Pancreatic fluid [H + ] = 1 x M C. _____ Sprite soft drink pH = 3.0 D. _____ pH = 7.0 E. _____ [OH - ] = 3 x M F. _____ [H + ] = 5 x *

Solution pH7 Identify each solution as 1. acidic 2. basic3. neutral A. _1__ HCl with a pH = 1.5 B. _2__ Pancreatic fluid [H + ] = 1 x M C. _1__ Sprite soft drink pH = 3.0 D. _3__ pH = 7.0 E. _1__ [OH - ] = 3 x M F. _2__ [H + ] = 5 x *

Acid Rain Unpolluted rain has a pH of 5.6 Rain with a pH below 5.6 is “acid rain“ CO 2 in the air forms carbonic acid CO 2 + H 2 O H 2 CO 3 Adds to H + of rain H 2 CO 3 H + (aq) + HCO 3 -(aq)* Formation of acid rain: 1. Emission of sulfur and nitrogen oxides from the burning of fuels expecially coal with high S content, power stations, oil refineries, vehicles as well as bacterial decomposition, and lighting hitting N 2 SO 2 26 million tons in 1980 NO and NO 2 22 million tons in 1980 Mt. St Helens (1980) 400,000 tons SO 2

Acid Rain Formation of acid rain: 1. Emission of sulfur and nitrogen oxides from the burning of fuels especially coal with high S content, power stations, oil refineries, vehicles as well as bacterial decomposition, and lighting hitting N 2 SO 2 26 million tons in 1980 NO and NO 2 22 million tons in 1980 Mt. St Helens (1980) 400,000 tons SO 2*

Acid Rain 2. Reactions in the atmosphere form SO 3 2SO 2 + O 2  2 SO 3*

Acid Rain 3. Reactions with atmosphere water form acids SO 3 + H 2 O  H 2 SO 4 sulfuric acid NO + H 2 O  HNO 2 nitrous acid HNO 2 + H 2 O  HNO 3 nitric acid*

Acid Rain 4. Effects of Acid Rain Decline in fish populations in rivers and lasts due to toxic effect of Al leached from soil by acid rain Extensive fish kills in spring from runoff due to accumulation of large amounts of acid on the snow Dissolves minerals Mg, Ca, and K from the soil and waxy coatings that protect leaves from bacteria Corrodes metals, textiles, paper and leather*

Sources of Acid Rain Power stations Oil refineries Coal with high S content Car and truck emissions Bacterial decomposition, and lighting hitting N 2*

Titration Acids and Bases Quantitative Analysis*

Acid/Base Titration Titration is an analytical method in which a standard solution is used to determine the concentration of another solution. Any solution for which the concentration is precisely known is called a standard solution. *

Titration

Titration Movie Before Endpoint At the Endpoint— Color persists for 30 s after swirling Over Titrated— missed endpoint— Start over!

Titrations (cont.) An acid/base titration uses the fact that one can be "neutralized" with the other. In this neutralization reaction, the acid and base will combine to produce a salt plus water. When done correctly, the resulting solution will be "neutral" - neither acid nor base. In a titration, this is known as the end point. The change in pH of the solution can be monitored using an indicator or pH meter. It is extremely important that the exact amounts of each solution used be known at the end point. *

Titration Curve This graph represents the titration of 10 ml of 0.1M HCl with 0.1M NaOH. The end point is characterized by a rapid change in pH with very little base added. *

Titration Problem Example: If 20 cm 3 of a 0.3 M solution of NaOH is required to neutralize 30.0 cm 3 of a sulfuric acid solution, what is the molarity of the acid solution? Solution Steps: 1.Write a balanced equation: 2NaOH + H 2 SO 4 Na 2 SO 4 + 2H 2 O 2.Determine the number of moles of the standard NaOH solution used: 3.Use the mole ratio from the balanced equation to convert moles of NaOH to moles of H 2 SO 4 : 4.Use the volume of acid solution used to determine the molarity of the acid solution: Notice that the 1dm3 / 1000cm 3 and the 1000cm3 / 1dm 3 will offset each other. You may shorten the problem by skipping these conversions.

THE END