Question

Properties of Buffers Lab.

I need help with problems 7 & 8. They’re pretty similar, but I’m confused on whether I’m doing them right.

I need to calculate the moles of HCl and NaOH and then somehow insert them into the log fraction in the Henderson Hasselbach formula, is that right?

Procedure (values are needed in procedure):

Part B Procedures: 1. Weigh about 3.5g of sodium acetate, record the exact mass on your data table and add it to a 150mL beaker. 2 Using a 10mL graduated cylinder measure 8.8mL of 3.0M acetic acid and add it to the beaker containing the sodium acetate. 3. Using a graduated cylinder measure 55.2mL of distilled water and add it to the solution in the beaker Stir the solution until all the sodium acetate is dissolved. 4. Calibrate the pH meter using the 4.00pH buffer solution. Click on the fone point calibration" option in the calibration menu. Measure the pH of your buffer solution. Determine the value of Ka for acetic acid using the pH of your buffer and the Henderson Hasselbach equation. Use the buffer solution you prepared for the next step. 5 Pour half (32mL) of the buffer solution into another 150mL beaker. Label the two beakers as 1 and 2 Pipette out 1.0mL of 6.0M HCI into beaker 1, mix and then measure the pH and record it. Remember to rinse the electrode between measurements. Pipette out 1.0mL of 6.0M NaOH into beaker 2, mix and measure the pH and record it I Calculations: 1. Calculate the Ka for acetic acid using the measured pH of your buffer solution. Compare the calculated value of Ka with the standard value of Ka for acetic acid, which is 1.8x10 2. Calculate the pH of the original buffer you prepared using the known value of Ka for acetic acid. 3. Calculate the pH of the buffer after the additions of HCI and NaOH 4. Compare the calculated values with the measured values.

Measured values during lab that I’ll be comparing #6/7/8 to:

Questions I need help with:

Answer 1

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Now PHE 4.7 45 L0q o 669- o.092. 0.4125+ O 0g2) - 4.745+ 109 0.577). (o5045) -4.74.5 + 0.058 = 4 02 pH sishtly derease ir (PH 4.9S NOCO just calulate number Here a moles q_NaoH: imi 6M N2OH we EAX W -u xlm) o O006 mdles O OO6 CN20H added1 O 65 Na oH is FOrmula strong ba se thus minus fram aid andwil add to its Concentratpon con. salb be ConcentTeIn sil1 oH 4.745 l0g salE] + Cao oldd- CA id NOH dded 4.745+ og (O669 t 0.0g2 ) (o-4125-O- 092) 4.745+ O- 375 pH 25 12O Slightly in (rease n PH buffea