hw5solution_pdf

# hw5solution_pdf - So(dds785 Homework 5 Sutclie(52440 This...

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So (dds785) – Homework 5 – Sutclife – (52440) 1 This print-out should have 22 questions. Multiple-choice questions may continue on the next column or page – Fnd all choices be±ore answering. Please note that ’p’ just equals ’negative log o±’ so we can have pH, pOH , pK a etc. 001 10.0 points Choose the pair o± concentrations that cannot be in a given aqueous solution at 25 C. 1. [H 3 O + ] = 10 14 M : [OH ] = 1 M 2. Any o± these could exist. correct 3. [H 3 O + ] = 10 M : [OH ] = 10 15 M 4. [H 3 O + ] = 10 7 M : [OH ] = 10 7 M 5. [H 3 O + ] = 10 3 M : [OH ] = 10 11 M Explanation: All o± these concentrations are possible. Re- call that pH can exist beyond the 1-14 range, but at 25 C, pH + pOH = 14 always applies. 002 10.0 points Which pH represents a solution with 1000 times higher [OH ] than a solution with pH o± 5? 1. pH = 7 2. pH = 4 3. pH = 6 4. pH = 5000 5. pH = 8 correct 6. pH = 3 7. pH = 1 8. pH = 2 9. pH = 0.005 Explanation: pH = 5 pOH = 14 - pH = 14 - 5 = 9 [OH ] = 10 pOH = 10 9 M [OH ] x = 1000 [OH ] = (10 3 )(10 9 M) = 10 6 M pOH x = - log(OH x ) = 6 pH x = 14 - pOH x = 14 - 6 = 8 003 10.0 points Sea water has a pH = 8.1. What is its hydro- nium ion concentration? 1. 1 . 3 × 10 6 M 2. 1 . 0 × 10 8 M 3. 7 . 9 × 10 9 M correct 4. 8 . 0 × 10 1 M 5. 5.9 M Explanation: 004 10.0 points At about what pH does pH = [H + ]? 1. pH = - 1.0 2. pH = 1.0 3. pH = 15.0 4. pH = 0.4 correct Explanation: [H + ] = 10 pH When pH = - 1 . 0, [H + ] = 10 When pH = 0.4, [H + ] = 10 0 . 4 = 0.40 When pH = 1.0, [H + ] = 10 1 When pH = 15.0, [H + ] = 10 15 005 10.0 points What is the pH o± a solution ±or which [OH ] equals 5 . 61 × 10 10 M?

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So (dds785) – Homework 5 – Sutclife – (52440) 2 Correct answer: 4 . 74896. Explanation: [OH] = 5 . 61 × 10 10 M pH = ? [H 3 O + ][OH ] = 1 . 0 × 10 14 M 2 [H 3 O + ] = 1 . 0 × 10 14 M 2 [OH ] = 1 . 0 × 10 14 M 2 5 . 61 × 10 10 M = 1 . 78253 × 10 5 M pH = - log[H 3 O + ] = - log(1 . 78253 × 10 5 ) = 4 . 74896 006 10.0 points How many grams oF HNO 3 are needed to give a pH oF 3 . 75 in an 11 . 5 L tank? The molar mass oF HNO 3 is 63 . 1 g/mol.
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hw5solution_pdf - So(dds785 Homework 5 Sutclie(52440 This...

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