The Acid Test Acids, Bases and pH

2. Describe the pH Scale The next few slides will illustrate this point. Be sure to write small and get it all!

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

pH Range [H+]>[OH-] [H+] = [OH-] [OH-]>[H+] 0 1 2 3 4 5 6 7 8 9 10 11 12 13 14 Neutral [H+]>[OH-] [H+] = [OH-] [OH-]>[H+] Acidic Basic

Learning Check pH7 Identify each solution as 1. acidic 2. basic 3. neutral A. _____ HCl with a pH = 1.5 B. _____ Pancreatic fluid pH = 8 C. _____ Sprite soft drink pH = 3.0 D. _____ pH = 7.0 E. _____ pH = 3 F. _____ pH = 12

Solution pH7 Identify each solution as 1. acidic 2. basic 3. neutral A. _1__ HCl with a pH = 1.5 B. _2__ Pancreatic fluid pH = 8 C. _1__ Sprite soft drink pH = 3.0 D. _3__ pH = 7.0 E. _1__ pH = 3 F. _2__ pH = 12

3. What is a hydronium ion? . . . . . . . . H H H . . . . . . . . Occasionally, in water, a H+ is transferred between H2O molecules . . . . . . . . H:O: + :O:H H:O:H + + :O:H- . . . . . . . . H H H water molecules hydronium hydroxide ion (+) ion (-)

4. How can the pH of a solution be determined? There will be several slides showing various ways to measure pH. Be sure to get them all!

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 Indicator Lower Color       Acid / Base Indicators Indicator Lower Color pH Range Upper Color methyl violet yellow-green 0.0 - 2.5 violet methyl orange red 2.5 - 4.4 yellow congo red blue 3.0 - 5.0 bromocresol green 4.5 - 5.5 methyl red 4.8 - 6.0 bromocresol purple 5.4 - 6.8 bromothymol blue 6.0 - 7.6 phenol red 6.4 - 8.2 red-violet cresol red 7.1 - 8.8 phenolphthalein colorless 8.3 - 10.0 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 R 9.9 - 11.8 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 [H3O+] 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.*

5. What are the properties of an acid? Acids Taste sour Donate a H+ pH less than 7 Turn litmus paper red Turn bromothymol blue to yellow Turn phenolphthalein colorless Neutralize bases

6. What are the properties of 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 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*

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*

7. What compounds are formed when an acid reacts with a base? 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 + H2O base acid salt water Ca(OH)2 + 2 HCl CaCl2 + 2H2O base acid salt water*

Learning Check N2 Select the correct group of coefficients for the following neutralization equations A. __ HCl + __ Al(OH)3 __AlCl3 + __ H2O 1) 1, 3, 3, 1 2) 3, 1, 1, 1 3) 3, 1, 1 3 B.__ Ba(OH)2 + __H3PO4 __Ba3(PO4)2 + __ H2O 1) 3, 2, 2, 2 2) 3, 3, 1, 6 3) 2, 3, 1, 6

Solution N2 A. 3HCl + 1Al(OH)3 1AlCl3 + 3H2O B. 3Ba(OH)2 + 2H3PO4 1Ba3(PO4)2 + 6H2O*

A practical use of the neutralization process 8. Antacids A practical use of the neutralization process

Antacids Used to neutralize stomach acid (HCl) Many contain one or more weak bases Alka-Seltzer: NaHCO3, citric acid, and aspirin Di-gel: CaCO3 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)2CO3 aluminum sodium dihydroxy carbonate Tums: CaCO3 Tempo: CaCO3, Al(OH)3, Mg(OH)2*

Which solution is more acidic the one with a pH of 2 or the one with a pH of 6? To answer this we are going to look at concentration and its effects on the environment.

pH measures the concentration of hydrogen ion [H+] in a solution So every time you increase one number on the pH scale the acidity (or alkalinity) increases by a power of 10! The concentration of pH = 2 solution is 4 pH values from a pH = 6 solution or The pH = 2 solution is 10,000 times more acidic than the pH = 6 solution

What does this mean for the environment? An in-depth look at acid rain

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 N2 SO2 26 million tons in 1980 NO and NO2 22 million tons in 1980 Mt. St Helens (1980) 400,000 tons SO2*

Acid Rain 2. Reactions in the atmosphere form SO3 2SO2 + O2  2 SO3*

Acid Rain 3. Reactions with atmosphere water form acids SO3 + H2O  H2SO4 sulfuric acid NO + H2O  HNO2 nitrous acid HNO2 + H2O  HNO3 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 N2*