Acid/Base Unit REVIEW ANSWERS

Practice defining acids and bases. WORTH YOUR TIME? 16 pts on 100 pt. test Looking at the formula Al(OH)3, we would assume that this is a base this has a pH of 7 this is an acid the concentration is stable According to the Bronsted-Lowry model, an base is a(n) H+ acceptor proton donor H+ ion producer OH- ion producer none of these Which represents a conjugate acid-base pair? H2O, H3O+ OH-, HNO3 H2SO4, SO42- HC2H3O2, C2H3O2- Identify the acid, base, conjugate acid, and conjugate base. H2SO4 + H2O --> H3O+ + HSO4- A B CA CB NH3 + H2O --> OH- + NH4+ B A CB CA

Differentiate between strong acid and weak acid. Individually: Read the following statement: Acids dissociate in water to form H+ ions. Some acids dissociate more readily than others. Strong acids dissociate completely to form the most H+ ions possible; while weak acids only dissociate partially. With your Partner: Where did you hear “strong acid” or “weak acid” used in this unit? Choose the correct answer: Solid hydrogen sulfate partially dissociates when added to water to produce an aqueous solution of HSO4- and H3O+. Therefore, sulfuric acid is a strong acid weak acid conjugate acid none of these

Understanding the Kw equation Individually: Write the kw equation. 1.0x10-14 = [H+][OH-] Write a sentence that explains when this equation should be used. With your Partner: Check your equation. Compare your explanations of the usefulness of this equation. Worth your time? 14 pts to 30 pts on 100 pt test

Understanding the pH equation Individually: Write the pH equation. pH = -log[H+] Write a sentence that explains when this equation should be used. Fill in the blanks: The pH scale goes from 0 to 14. Acids have a pH below 7, and bases have a pH above 7. With your Partner: Check your equation. Compare your explanations and answers to the fill in the blank statement. Worth your time? 21 pts on 100 pt test

Understanding the pOH equation Individually: Write the pOH equation. pOH = -log[OH-] Write a sentence that explains when this equation should be used. How is the pOH equation different from the pH equation? With your Partner: Check your equation. Compare your explanations. Worth your time? 16 pts on 100 pt test

Understanding the relationship between pH and pOH Individually: pH + pOH = 14 Write the equation that includes both pH and pOH. Write a sentence that explains when this equation should be used. With your Partner: Check your equation. Compare your explanations. Worth your time? 16 pts on 100 pt test

Practice Kw, pH, and pOH calculations. Check your answers to yesterday’s handout. Solve. During the course of the day, human saliva varies between acidic and basic. What is the [H+] in saliva if [OH-] is 3.16x10-8M? What is the pH of the saliva? At this point in the day, is it acidic, basic, or neutral? [H+] =3.16x10-7 M, pH = 6.5, acidic What is the concentration of OH- ions in 0.1M bicarbonate of soda if [H3O+] is 3.98x10-9M? Is the bicarbonate acidic, basic, or neutral? What is the pH? What is the pOH? [OH-]=2.51x10-6M, pOH=5.6, pH=8.4, basic What is the concentration of H3O+ ions in eggs if [OH-] is 6.0x10-7M? Are eggs acidic, basic, or neutral? [H+] = 1.67x10-8 M, basic If the pH of a solution is 6.4, what is the [OH-]? [OH-] = 2.51x10-8 M Find the [H+] and [OH-] of a solution with a pH of 3.494. [H+] = 3.2x10-4 M, [OH-] =3.1x10-11 M For each pair of concentrations, tell which represents the more acidic solution. [H+] = 0.000013 M or [OH-] = 0.0000032 M [H+] = 1.03x10-6 M or [OH-] = 1.54x10-8 M

Understanding titrations Individually: Fill in the blanks. Every time that an acid and a base react in a neutralization reaction, a salt and water are produced. Solve: A volume of 20-mL of 0.25M Al(OH)3 neutralizes a 75-mL sample of H2SO4 solution. What is the concentration of the acid? 2Al(OH)3 + 3H2SO4  6H2O + Al2(SO4)3, Acid M = 0.1 M Solve: Calculate how many milliliters of 0.30M H2SO4 must be added to titrate 75 mL of 0.10 M KOH. H2SO4 + 2KOH  2H2O + K2SO4, 0.025 L or 25mL of acid With your Partner: Check your fill in the blank statement. Compare your balanced equations with your partner. Compare your work and answers to the two calculations. NOTE: IF SOMEONE HAS TOLD YOU ABOUT A SHORT-CUT (MAVA = MBVB), FORGET IT. IT DOES NOT WORK CONSISTENTLY. Worth your time? 10 pts on 100 pt test