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ACID/BASE UNIT REVIEW ANSWERS

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Practice defining acids and bases. Looking at the formula Al(OH) 3, we would assume that a) this is a base b) this has a pH of 7 c) this is an acid d) the concentration is stable According to the Bronsted-Lowry model, an base is a(n) a) H+ acceptor b) proton donor c) H + ion producer d) OH - ion producer e) none of these Which represents a conjugate acid-base pair? a) H 2 O, H 3 O + b) OH -, HNO 3 c) H 2 SO 4, SO 4 2- d) HC 2 H 3 O 2, C 2 H 3 O 2 - Identify the acid, base, conjugate acid, and conjugate base. H 2 SO 4 + H 2 O --> H 3 O + + HSO 4 - A B CA CB NH 3 + H 2 O --> OH - + NH 4 + B A CB CA WORTH YOUR TIME? 16 pts on 100 pt. test

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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 HSO 4 - and H 3 O +. Therefore, sulfuric acid is a a) strong acid b) weak acid c) conjugate acid d) none of these

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Understanding the K w equation Individually: Write the k w 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

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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

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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

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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

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Practice K w, 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 -8 M? 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 [H 3 O + ] is 3.98x10 -9 M? Is the bicarbonate acidic, basic, or neutral? What is the pH? What is the pOH? [OH-]=2.51x10 -6 M, pOH=5.6, pH=8.4, basic What is the concentration of H 3 O + ions in eggs if [OH - ] is 6.0x10 -7 M? 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. 1.[H + ] = 0.000013 M or [OH - ] = 0.0000032 M 2.[H + ] = 1.03x10 -6 M or [OH - ] = 1.54x10 -8 M

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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 H 2 SO 4 solution. What is the concentration of the acid? 2Al(OH) 3 + 3H 2 SO 4 6H 2 O + Al 2 (SO 4 ) 3, Acid M = 0.1 M Solve: Calculate how many milliliters of 0.30M H 2 SO 4 must be added to titrate 75 mL of 0.10 M KOH. H 2 SO 4 + 2KOH 2H 2 O + K 2 SO 4, 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 (M A V A = M B V B ), FORGET IT. IT DOES NOT WORK CONSISTENTLY. Worth your time? 10 pts on 100 pt test

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