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
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Piedmont Hills High School - AP Chemistry Phan, Madalyn Period , Laboratory Experiment : Buffer Lab DATA Buffers Initial pH (given by ph meter, not calculations) pH after first trial with HCl (100ml) pH after second trial HCl (150ml) pH after first trial with NaOH (0.400g) pH after second trial with NaOH (0.600g) High Conc. 4.690 3.890 3.330 5.360 12.59 Low Conc. 4.620 1.970 1.410 13.35 13.43 Different Conc. 4.270 1.920 1.410 6.070 12.07 Strong Acid and its salt 0.5700 0.4000 0.8000 13.80 13.99 CALCULATIONS High concentration buffer pH change after 100ml 0.1 HCl added: 4.690 - 3.890 = 0.8 pH change 150ml 0.1 HCl added: 4.690 - 3.330 = 1.36 pH change 0.400g NaOH added: 5.360 - 4.690 = 0.67 pH change 0.600g NaOH added: 12.590 - 4.690 = 7.9 pH change Low concentration buffer pH change after 100ml 0.1 HCl added: 4.620 - 1.970 = 2.650 pH change 150ml 0.1 HCl added: 4.620 - 1.410 = 3.210 pH change 0.400g NaOH added: 13.35 - 4.620 = 8.73 pH change 0.600g NaOH added: 13.43 - 4.620 = 8.81 pH change Different concentration buffer pH change after 100ml 0.1 HCl added: 4.270 - 1.920 = 2.350 pH change 150ml 0.1 HCl added: 4.270 - 1.410 = 2.860 pH change 0.400g NaOH added: 6.070 - 4.270 = 1.800 pH change 0.600g NaOH added: 12.070 - 4.270 = 7.800 pH change Strong acid buffer pH change after 100ml 0.1 HCl added: 0.740 - 0.570 = 0.170 pH change 150ml 0.1 HCl added: 0.800 - 0.570 = 0.230 pH change 0.400g NaOH added: 13.80 - 0.570 = 13.23 pH change 0.600g NaOH added: 13.99 - 0.570 = 13.42 pH change
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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
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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
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