How do you make 0.2M citrate buffers for pH 1 1.5 2 2.5 3 3.5 4 4.5 5 5.5 6 6.5 and 7?

Answer 1

------Headings-------- pH Total conc. (M) Conjugate Base Conc. Conjugate Acid Conc. Conjugate Base Conjugate Acid -------------------------- 1.0 0.2 0.00141 0.19859 Dihydrogen Citrate Citric Acid 1.5 0.2 0.00438 0.19562 Dihydrogen Citrate Citric Acid 2.0 0.2 0.01322 0.18678 Dihydrogen Citrate Citric Acid 2.5 0.2 0.03658 0.16342 Dihydrogen Citrate Citric Acid 3.0 0.2 0.08290 0.11710 Dihydrogen Citrate Citric Acid 3.5 0.2 0.13825 0.06175 Dihydrogen Citrate Citric Acid 4.0 0.2 0.02903 0.17097 Hydrogen Citrate Dihydrogen Citrate 4.5 0.2 0.06988 0.13012 Hydrogen Citrate Dihydrogen Citrate 5.0 0.2 0.12588 0.07412 Hydrogen Citrate Dihydrogen Citrate 5.5 0.2 0.16860 0.03140 Hydrogen Citrate Dihydrogen Citrate 6.0 0.2 0.05695 0.14305 Citrate Hydrogen Citrate 6.5 0.2 0.11146 0.08854 Citrate Hydrogen Citrate 7.0 0.2 0.15985 0.04015 Citrate Hydrogen Citrate Since citric acid has three pKa's (3.15, 4.77, 6.40), , the one closest to each desired pH should be used to make the buffer. For example, if a pH 4.9 buffer is desired, the second pKa should be used and the conjugate acid/base pair for this pKa is dihydrogen citrate and hydrogen citrate. Each of these conjugate acid/base concentrations can be multiplied by the overall volume desired to get the desired volume. However, if not all four compounds are readily available (which is quite common), each one can be generated with acid/base chemistry. For example, if only 1.0 M citric acid is available and 100 ml of 0.2 M pH 7.0 buffer is required, 0.2*0.100/1.0 = 0.02 L or 20 ml of citric acid should be used and (0.15985*3+0.04015*2) *0.100/1.0= 0.055985 L or 55.985 ml of 1.0 NaOH should be added to the citric acid to make the required amount of citrate and hydrogen citrate. This makes up for 75.985 ml and the rest 24.015 ml should be topped up with distilled water.

Answer 2

How do you prepare citrate buffer of pH 5.5