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# HW5_pdf - leazenby(jl35875 – Homework 5 – Sutcliffe...

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Unformatted text preview: leazenby (jl35875) – Homework 5 – Sutcliffe – (52440) 1 This print-out should have 22 questions. Multiple-choice questions may continue on the next column or page – find all choices before answering. Please note that ’p’ just equals ’negative log of’ so we can have pH, pOH , pK a etc. 001 10.0 points Choose the pair of concentrations that cannot be in a given aqueous solution at 25 ◦ C. 1. [H 3 O + ] = 10 − 3 M : [OH − ] = 10 − 11 M 2. [H 3 O + ] = 10 − 14 M : [OH − ] = 1 M 3. Any of these could exist. correct 4. [H 3 O + ] = 10 − 7 M : [OH − ] = 10 − 7 M 5. [H 3 O + ] = 10 M : [OH − ] = 10 − 15 M Explanation: All of 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 of 5? 1. pH = 5000 2. pH = 3 3. pH = 1 4. pH = 2 5. pH = 6 6. pH = 4 7. pH = 0.005 8. pH = 7 9. pH = 8 correct 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 . × 10 − 8 M 2. 1 . 3 × 10 − 6 M 3. 8 . × 10 − 1 M 4. 5.9 M 5. 7 . 9 × 10 − 9 M correct Explanation: 004 10.0 points At about what pH does pH = [H + ]? 1. pH = 0.4 correct 2. pH = 15.0 3. pH =- 1.0 4. pH = 1.0 Explanation: [H + ] = 10 − pH When pH =- 1 . 0, [H + ] = 10 When pH = 0.4, [H + ] = 10 − . 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 of a solution for which [OH − ] equals 7 . 34 × 10 − 10 M? leazenby (jl35875) – Homework 5 – Sutcliffe – (52440) 2 Correct answer: 4 . 8657. Explanation: [OH] = 7 . 34 × 10 − 10 M pH = ?...
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HW5_pdf - leazenby(jl35875 – Homework 5 – Sutcliffe...

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