Acids and Bases

tasteyoursmoothie.wordpress.com en.wikipedia.org Soda.com Soap.com Which of these items does not belong to the group and why?

en.wikipedia.org proctorandgamble.com drano.com Which of these items does not belong to the group and why? walmart.com

Acids and Bases What are acids and bases? Acids and Bases are one way of classifying matter through its properties.

Properties of Acids – Taste sour – Change blue litmus paper to red color – pH less than 7 – Reacts with carbonates and bicarbonates forming CO 2 gas – React with metals to form a salt compound and H 2 gas (pop!) – electrolyte chemwiki

Reacts with carbonates and bicarbonates forming CO 2 gas MgCO 3(s) + 2HCl (aq) → MgCl 2(aq) + H 2 O (l) + CO 2(g) carbonate acid salt water carbon dioxide *Remember that you can test for CO 2 using a burning splint. The CO 2 gas will put out the flame of the burning splint.

React with metals to form a salt compound and hydrogen gas (pop!) 2 HCl + Mg  MgCl 2 + H 2 acid metal salt hydrogen gas *Remember that you can test for H 2 using a burning splint. The H 2 gas will make a popping sound and put out the flame of the burning splint.

Electrolytes - chemicals that dissociate when in water Dissolve Dissociate

Name of acidChemical formulaCommon use or location Hydrochloric acidHClGastric juice Sulfuric acid H 2 SO 4 Car batteries Nitric acid HNO 3 fertilizer Carbonic acidH 2 CO 3 Soft drinks Uric acidC5H4N4O3C5H4N4O3 urine Ascorbic acid (Vitamin C)C6H8O6C6H8O6 fruit Citric acidC6H8O7C6H8O7 Citrus fruit Acetic acidHC 2 H 3 O 2 vinegar Tartaric acidC4H6O6C4H6O6 grapes

Properties of bases – Taste bitter – Feel slippery – Change red litmus paper to blue color – pH greater than 7 – electrolyte

Neutral solutions Substances that are neither acids nor bases do not change the color of red or blue litmus paper pH equals 7 nonelectrolytes chemwiki

Arrhenius Definition of Acids Arrhenius acids - give (donate) hydrogen ions (H + ) in aqueous solution. *an H + ion is a proton HCl + H 2 O  H 3 O + + Cl - Example: What happened to the H of HCl? Which substance is the acid: HCl or H 2 O? How do you know?

Arrhenius bases – give (donate) hydroxide ions (OH) -1 in aqueous solution. NaOH (aq)  Na + + (OH) - Example: What happened to NaOH when it was added to water? Why is NaOH classified as an Arrhenius base? studentweb.usq.edu.au

Practice Using the Arrhenius definition, classify the following as an acid or a base in water 1.HI 2.KOH 3.HNO 3 4.Ca(OH) 2 5.H 2 SO 4 6.Mg(OH) 2 Acid, in water HI  H + + I - Acid, in water HNO 3  H + + NO 3 - Base, in water KOH  K + + OH - Base, in water Ca(OH) 2  Ca OH - Base, in water Mg(OH) 2  Mg OH - Acid, in water H 2 SO 4  2H + + SO 4 -2

Arrhenius definition of acids and bases is limited.

Brönsted-Lowry Definition of Acids and Bases Acids donate a proton or H + (proton donor) Bases takes in a proton or H + (proton acceptor)

NH 3 is accepting an H + so it is a B-L base.

Brönsted-Lowry Definition of Acids and Bases A conjugate base is the remainder of the original acid, after it donates its hydrogen ion A conjugate acid is the particle formed when the original base gains a hydrogen ion For example: conjugate Leftovers from acid Base that has gained an H +

Practice: Brönsted-Lowry Acids and Bases Identify the B-L acid (a), conjugate base (c.b.), B-L base (b), and conjugate acid (c.a.) 1. HCl + H 2 O ↔ H 3 O + + Cl - 2. HNO 2 + H 2 O ↔ H 3 O + + NO SO H 2 O ↔ HSO OH - Ans: acid + base ↔ c.a. + c.b Ans: base + acid ↔ c.a. + c.b

Review In a B-L acid-base reaction: What happens to an acid? What happens to the base? What is a conjugate base? What is a conjugate acid? Lost the proton (H + ) gained the proton (H + ) Acid without the proton (H + ) Base with the proton (H + )

More Practice: Brönsted-Lowry Acids and Bases Identify the acid, conjugate base (c.b.), base, and conjugate acid (c.a.) 1. HC 2 H 3 O 2 + H 2 O ↔ H 3 O + + C 2 H 3 O CO H 2 O ↔ HCO OH - 3. NH H 2 O ↔ NH 3 + H 3 O + Ans: acid + base ↔ c.a. + c.b Ans: base + acid ↔ c.a. + c.b Ans: acid + base ↔ c.b. + c.a

The pH concept Acidic Alkaline (basic) Neutral

pHpH (8:53) formula: pH = -log[H + ] [H + ] = concentration of H + ions

Example 1: What is the pH of a solution with [H + ] = 1 x M? formula: pH = -log[H + ] where [H + ] = concentration of H + ions Example 2: What is the pH of a solution with [H + ] = 1 x M?

The pH concept 1. [H + ] = 0.01 M 2. H + ] = M 3. [H + ] = M 4. [H + ] = M 5. [H + ] = 3.2 x M 6. [H + ] = 6.5 x M 7. [H + ] = 4.5 x M pH = 2, acid Practice: Find the pH of the following solutions and state whether the solution is an acid, base or neutral. pH = 4, acid pH = 1.8, acid pH = 9.5, base pH = 3.2, acid pH = 7, neutral pH = 7.3, base

pH scale 26 [H + ] [OH - ] 14 0

What is the difference in the dissociation of strong and weak acids? s-owl.cengage.com

Strong Acids and Bases Strong acids completely dissociate and release [H + ] ions. HCl  H + + Cl - Strong bases completely dissociate and release [OH - ] ions. NaOH  Na + + OH - These are the ONLY strong acids: HCl, HBr, HI, HNO 3, HClO 4, H 2 SO 4 Some strong bases – NaOH, KOH, LiOH

Particle diagrams 29 strong acid – complete dissociation weak acid – partial dissociation

Comparison between Solutions of Strong and Weak Acids Two solutions are represented by the diagram below. Which diagram illustrates a solution of a weak acid? How do you know? s-owl.cengage.com AB

H + concentration of Strong and Weak Acids en.wikibooks.org How is the pH related to the H + ion concentration of weak and strong acids?

Concentrated vs. Dilute Concentrated acids and bases have a relatively large # of moles (of acid or base) per liter of solution. Dilute acids and bases have a relatively small # of moles (of acid or base) per liter of solution M HF is more concentrated than 2.0 M HF. 2.0 M KOH is more dilute than 10.0 M KOH. 34

Two acids, HCl and HC 2 H 3 O 2 are both 0.10 M. Which of the two has a higher pH and why? H + Concentration of Strong and Weak Acids A B

Acid Base Concentration Molarity- The number of moles of solute dissolved in 1.00 L of solution Molarity (M) = Moles of solute Liter of solution Example: What is the molarity if 2.0 moles of hydrochloric acid are added to 5.0 L of solution? M = 2.0 mol = 0.40 M 5.0 L 36

Diluting Solutions Diluting Solutions: V 1 M 1 = V 2 M 2 Example: What volume of 2.0 M H 2 SO 4 would you need to prepare 100. mL of 0.40 M H 2 SO 4 ? V 1 = x M 1 = 2.0M (x)(2.0) = (100)(0.40) V 2 = 100.ml x = 20 mL M 2 = 0.40 M 37

Indicators Chemicals that change color in the presence of an acid or a base Used to determine the pH of a solution Examples: litmus paper (red and blue), pH paper, phenolphthalein, red cabbage juice catalog.flatworldknowledge.com

Indicators

Acid Vocabulary Binary acid – acid that contains only H and one other type of atom Ex. HBr, H 2 S Ternary acid – acid that contains H and a polyatomic ion Ex. H 2 SO 4 Monoprotic acid – acid that only has one H atom Ex. HBr, HI Polyprotic acid – acid that has more than one H atom Ex. H 2 S, H 3 PO 4 *a hydrogen ion, H +, is a proton

Naming AcidsNaming Acids (stop at 5:47) No Oxygen  w/Oxygen Examples:HCl – hydrochloric acid HClO 3 – chloric acid HClO 2 – chlorous acid binary ternary

Naming Acids binary

Practice Name the following acids: 1.HI 2.HF 3.H 2 SO 4 4.H 2 SO 3 5.H 2 CO 2 Write the chemical formula: 1.Hydrobromic acid 2.Hydrosulfuric acid 3.Acetic acid 4.Phosphoric acid 5. Nitrous acid Hydroiodic acid Hydrofluoric acid sulfuric acid sulfurous acid carbonic acid H2SH2S HC 2 H 3 O 2 H 3 PO 4 HNO 2 HBr Symbol, ox #, criss-cross

Hydroxides (OH - ) NaOH sodium hydroxide Mg(OH) 2 magnesium hydroxide Al(OH) 3 aluminum hydroxide Base Nomenclature Ammonia - NH 3 is a common base found in household glass cleaners. Most bases are named the same as any other ionic compound, for example :

Writing formulas for bases Just like all ionic compounds, write the symbol for each ion, its oxidation number, and then criss-cross to get the subscripts. Example: potassium hydroxide K +1 (OH) -1 KOH or K(OH)

Practice writing formulas for bases 1.Zinc hydroxide 2. Iron (II) hydroxide 3. Calcium hydroxide 4. Lithium hydroxide

Neutralization one type of double replacement reaction Reactants are acid and base, products are salt and water Acid + Base  Salt + water HCl + NaOH  NaCl + H 2 O 47

TitrationTitration (6:52) A controlled acid-base neutralization reaction The process of finding the concentration of an unknown solution by using a certain volume of a known concentration solution.

49 This solution is also called the analyte or titer Unknown concentration known concentration

End point of a titration The point where neutralization is achieved Occurs just before the indicator has changed color DETERMINED BY OBSERVATION, DURING THE TITRATION EXPERIMENT 50

51

Equivalence Point the stoichiometric end point of a titration when moles of H + from acid = moles of OH - from base DETERMINED FROM THE DATA COLLECTED IN THE TITRATION EXPERIMENT

Neutralization Problems- (#H + )M A V A = M B V B (#OH - ) #H + = #H in chemical formula M A = molarity of acid V A = volume of acid M B = molarity of base V B = volume of base #OH - = #OH in chemical formula 53

Practice: Neutralization Problem (#H + )M A V A = M B V B (#OH - ) When 45.0 mL of 3.00 M HBr is added to 80.0 mL of Ca(OH) 2 What is the molarity of the Ca(OH) 2 that was neutralized? #H + = M A = V A = M B = V B = #OH - = 54

Practice: Neutralization Problem (#H + )M A V A = M B V B (#OH - ) In a titration experiment, if 65.0 mL of an HCl solution reacts with 47.2 mL of a 0.65-M NaOH solution, what is the concentration of the HCl solution? #H + = M A = V A = M B = V B = #OH - = 55

Ion Stoichiometry : ) H 2 SO 4 + 2NaOH  Na 2 SO 4 + 2H 2 O 240 grams of NaOH react with sulfuric acid. How many moles of H + ions are consumed?