ANSWERS CHEM 1420 Test 2 and EXTRA CREDIT

ANSWERS CHEM 1420 Test 2 and EXTRA CREDIT - Your name _...

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Your name _______________________________________ 1420-002 HOUR TEST -- April 1, 2011 _____ 1. What is the conjugate base of H 2 CO 3 ? HCO 3 -1 To find the conjugate base, remove H + . _____ 2. Knowing that the K b of a base C 4 H 9 O 2 -1 is 4.6 x 10 -6 , what is the pH of a 0.040 M solution of the conjugate acid C 4 H 10 O 2 ? 5.03 K a K b = 1 x 10 -14 K a = (1 x 10 -14 )/(4.6 x 10 -6 ) = 2.17 x 10 -9 K a = 2.17 x 10 -9 = x 2 /0.040 x = [H + ] = 9.32 x 10 -6 pH = -log[H + ] = -log[9.32 x 10 -6 ] = 5.03 _____ 3. What is the pH of a solution prepared by mixing 1.50 g of acetic acid in 1.00 liter of solution? 3.17 [HZ] = (1.50 g)/(60.05 g/mol) = 0.0250 K a = 1.8 x 10 -5 = x 2 /(0.025) x = [H + ] = 6.70 x 10 -4 pH = -log[6.70 x 10 -4 ] = 3.17 ____ 4. What is the pH of a 2.00 x 10 -3 M solution of HNO 3 ? 2.70 Strong acid: pH = -log[2.00 x 10 -3 ] = 2.70 _____ 5. What is the pH of a 0.025 M solution of sodium acetate? 8.57 K a K b = 1 x 10 -14 (1.8 x 10 -5 ) K b = 1 x 10 -14 K b = 5.56 x 10 -10 = x 2 /(0.025) x = [OH -1 ] = 3.73 x 10 -6 pOH = 5.43 pH = 8.57 _____ 6. What is the pH of a solution prepared by mixing 0.0050 mole of acetic acid and 0.0030 mole sodium acetate in 1.00 L of solution? 4.52 pH = pK a + log[base/acid] --- pK a = -log[1.8 x 10 -5 ] = 4.74 pH = 4.745 + log[0.005/0.003] = 4.52
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_____ 7. The pH of a NaHCO
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ANSWERS CHEM 1420 Test 2 and EXTRA CREDIT - Your name _...

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