2 The 25 mL was deposited into a 100 mL beaker 3 Steps 1 and 2 were repeated

# 2 the 25 ml was deposited into a 100 ml beaker 3

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2. The 25 mL was deposited into a 100 mL beaker 3. Steps 1 and 2 were repeated, for a total of 2 separate beakers of 25 mL 4. 0.400 g NaOH were measured out using a scale and added to the 100 mL beaker and mixed in using the glass stirring rod 5. The pH was measured using a pH meter and recorded 6. 0.600 g NaOH were measured out using a scale and added to the 100 mL beaker and mixed in using the glass stirring rod 7. The pH was measured using the pH meter and recorded  Piedmont Hills High School - AP Chemistry Phan, Madalyn Period , Laboratory Experiment : Buffer Lab ANALYSIS AND DISCUSSION 1. For each buffer you prepared, calculate the (a) amount of solid sodium hydroxide and (b) volume of the 0.10 M hydrochloric acid needed to change the pH of the buffer by one High Concentration a) .69 og [ H ] 4 = l + Initial amount of : H ] [ + H ] .04 0 [ + = 2 × 1 −5 .69 og [ H ] 5 = l + Needed amount of : H ] [ + H ] .04 0 [ + = 2 × 1 −6 2.04 0 ) 2.04 0 ) ( × 1 −5 − ( × 1 −6 Amount of needed to get rid of: H ] [ + .84 0 1 × 1 −5 .84 0 M 1 × 1 −5 = 0.200 moles [ H ] + .68 0 mole H 3 × 1 −6 + NaOH needed to raise the 3.68 0 mole H )( )( ) .47 0 g ( × 1 −6 + 1 mol H + 1 mol NaOH 40 g NaOH 1 mol NaOH = 1 × 1 −4 pH by one b) .69 og [ H ] 3 = l + 100 mL HCl lowered the pH by 0.8 100/0.8 = 125 mL of 0.1 M HCl needed to lower the pH by 1 Low Concentration a) .62 og [ H ] 4 = l + Initial amount of : H ] [ + H ] .40 0 [ + = 2 × 1 −5 .62 og [ H ] 5 = l + Needed amount of : H ] [ + H ] .40 0 [ + = 2 × 1 −6 2.40 0 ) 2.40 0 ) ( × 1 −5 − ( × 1 −6 Amount of needed to get rid of: H ] [ + .16 0 2 × 1 −5 .16 0 M 2 × 1 −5 = 0.100 L moles [ H ] + .16 0 mole H 2 × 1 −6 + NaOH needed to raise the pH by one 2.16 0 )( )( ) .64 0 g ( × 1 −6 1 mol H + 1 mol NaOH 40 g NaOH 1 mol NaOH = 8 × 1 −5 b) .69 og [ H ] 3 = l + 100 mL HCl lowered the pH by 2.65 100/2.65 = 37.7 mL of 0.1 M HCl needed to lower the pH by 1 Different Concentration a) .27 og [ H ] 4 = l + Initial amount of : H ] [ + H ] .37 0 [ + = 5 × 1 −5 .27 og [ H ] 5 = l + Needed amount of : H ] [ + H ] .37 0 [ + = 5 × 1 −6 5.37 0 ) 5.37 0 ) ( × 1 −5 − ( × 1 −6 Piedmont Hills High School - AP Chemistry Phan, Madalyn Period , Laboratory Experiment : Buffer Lab Amount of needed to get rid of: H ] [ + .83 0 4 × 1 −5 .83 0 M 4 × 1 −5 = 0.100 L moles [ H ] + .83 0 mole H 4 × 1 −6 + NaOH needed to raise the 4.83 0 mole H )( )( ) .93 0 g ( × 1 −6 + 1 mol H + 1 mol NaOH 40 g NaOH 1 mol NaOH = 1 × 1 −4  #### You've reached the end of your free preview.

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• Fall '13
• pH, Phan, Madalyn, Piedmont Hills High School
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