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11 Nov 2019
Locker number: 1045
2. a) How does an acid-base indicator function? b) Heptamethoxy red has a Ka = 1.26 à 10° and undergoes a colour change from] red to What is the approximate pH range for colourless as a solution becomes more basic. which this indicator is useful? 3. a) Define pH buffer solution and, in gencral tems, state its composition List two in your day-to-day life. examples of pH buffered systems buffer capacity. Explain how each objective is achieved. In part B-3 of the procedure, you are required to prepare two different buffered solutions, b) A well designed buffer achieves two objectives: i. the desired pH value; and ii. effective 4. one acidic and one neutral, using the following reagents: Buffer Weak acid (15.0 mL) Conjugate base (x mL) 0.100 M HC H3O2 (acetic acid, Ka 1.8x10) 0.100 M NaC2H5O2 (sodium acctate) a) acidic 0.100 MNaH PO4 (sodium hydrogen phosphate, Ka- 6.2x 10) 0.100 M Na HP04 (disodium phosphate) b) neutral Your target pH values are assigned in accordance with the first digit of your locker number First digit of locker number Acidic buffer Neutral buffer 3.80 3.90 4.00 4.10 4.20 4.30 4.40 4.50 6.00 6.20 6.40 6.60 6.80 7.00 7.20 7.40 4 fyour locker number is 5017, for example, you would prepare buffers of pH 4.20 and 6.80 For each buffer, calculate the volume (x ml) of conjugate base that must be added to 15.0 mL of the corresponding acid. (Retain a copy of your answers.)
Locker number: 1045
2. a) How does an acid-base indicator function? b) Heptamethoxy red has a Ka = 1.26 à 10° and undergoes a colour change from] red to What is the approximate pH range for colourless as a solution becomes more basic. which this indicator is useful? 3. a) Define pH buffer solution and, in gencral tems, state its composition List two in your day-to-day life. examples of pH buffered systems buffer capacity. Explain how each objective is achieved. In part B-3 of the procedure, you are required to prepare two different buffered solutions, b) A well designed buffer achieves two objectives: i. the desired pH value; and ii. effective 4. one acidic and one neutral, using the following reagents: Buffer Weak acid (15.0 mL) Conjugate base (x mL) 0.100 M HC H3O2 (acetic acid, Ka 1.8x10) 0.100 M NaC2H5O2 (sodium acctate) a) acidic 0.100 MNaH PO4 (sodium hydrogen phosphate, Ka- 6.2x 10) 0.100 M Na HP04 (disodium phosphate) b) neutral Your target pH values are assigned in accordance with the first digit of your locker number First digit of locker number Acidic buffer Neutral buffer 3.80 3.90 4.00 4.10 4.20 4.30 4.40 4.50 6.00 6.20 6.40 6.60 6.80 7.00 7.20 7.40 4 fyour locker number is 5017, for example, you would prepare buffers of pH 4.20 and 6.80 For each buffer, calculate the volume (x ml) of conjugate base that must be added to 15.0 mL of the corresponding acid. (Retain a copy of your answers.)
Tod ThielLv2
2 Feb 2019