A 0.1 M Tris bufer was made with a pH of 8.0 at 20°C. You will be using this buf
ID: 204835 • Letter: A
Question
A 0.1 M Tris bufer was made with a pH of 8.0 at 20°C. You will be using this bufer in a cold room whose temperature is 10°C. What would the pH of the bufer be at 10°C?
Buffering Agent Properties (HEPES and Tris are by far the most commonly used) Formula ApKaeC Weight Thermal Coefficient pKa (4 °C) pKa (20 °C) pKa Common Name Bicine 63.17 0.018 221.31 0.021 207.290011 238.31 0.014 252.33 0.011 213.26 0.01 209.27 0011 0237 00085 79.17 0.021 121.14 0.031 8.64 10.74 9.73 7.77 8.18 6.33 7.38 6.94 8.49 8.80 8.35 10.40 9.55 755 8.04 0.0 9.36 7.31 7.81 5.96 7.01 6.66 7.79 7.77 5 6.15 7.20 6.80 8.15 8.30 MOPS TricineExplanation / Answer
The ionization enthalpy of the buffer determines the extent of the pKa change with temperature, and, therefore, the change in solution pH with temperature. The ionization enthalpy for Tris is quite high and that is the reason for the considerable temperature dependency of pH in Tris solutions. From the studies pKa changes -0.028 pH units for each degree Celsius when temperature increases.
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