assignment4

# assignment4 - Assignment Buffers Indicators 1 Buffers and...

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Assignment: Buffers & Indicators 1 Buffers and Indicators MSDS: Sodium acetate This should be included in the EXPERIMENTAL section. Include the following items, if possible. Hazards : Handling and storage: Disposal: SAMPLE CALCULATION: 1. R1 and R2 are defined in the preformatted spreadsheet. The expression for R2 is derived in the lab manual. Using the same method, derive the expression for R2. 2. Show how one of the K HIn values is calculated. PRELABORATORY QUESTIONS: 1. List all the common strong acids. What distinguishes strong acid from weak acid in aqueous medium? Write two reactions, first let HA be a strong acid then a weak acid. 2a. Calculate the pH of a 48-mL 0.10 M HCl aqueous solution. Ans . 1.0 2b. Calculate the pH of a 48-mL 0.10 M HCl and 2.0-mL of bcg mixture. Ans . 1.02 3a. The Henderson-Hasselbalch (HH) equation is ] Acid [ ] Base [ log pK pH a + = Use this equation to calculate the volumes of 0.10 M acetic acid and 0.20 M sodium acetate that are needed to prepare 48-mL buffer solution with pH = 3.70. K a for acetic acid is 1.75 x 10 -5 . Ans . and mL 0 . 46 V HAc = mL 0 . 2 V Ac = 3b. After the buffer solution is prepared, 2.0-mL of bcg is mixed in. What is the new pH value? Ans . No change 3c. If 1.0-mL of 1.0M NaOH is added to the solution, what will be the new pH value? Ans. 4.35 POSTLABORATORY QUESTIONS: Here is the second way of getting the equilibrium constant of the indicator using the same experimental data. Before proceeding to solve the problem, some background information is needed.

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