D. Plot the measured pH vs. the total mmoles of OH-added after each addition on the same graph (start plotting at the middle of the graph).
6 Answer 0 / 1 / 2 Answer 0 / 1 Answer 0 / 1 Explanation 0 / 1 Explanation 0 / 1 ________pts / 6 pts E. The buffer capacityof a solution is defined as the number of moles of H+(or OHrequired to change the pH of the solution by one pH unit(for example, the number of moles of acid required to change the pH from 4.76 to 3.76 or the number of moles of base required to change the pH from 4.76 to 5.76). It is a measure of how well a buffer works. From your graph, determine the buffer capacity of the acetic acid/sodium acetate buffer (your answer will be either mmoles of H+ or OH–required to change the pH by exactly 1 pH unit). Perhaps an average of both values would be best. - ) F. How much did the pH change during the addition of the first mL of acid (or base)? How much did the pH change during the addition of the third mL of acid (or base)? Note: this is the pH change between 2.0 and 3.0 mmoles on the graph. What does this titration tell you about buffers and buffer action relative to the pKa? Why is the magnitude of the pH change greater with each increment of added H+ (or OH – )?
7 Work 0 / 1 / 2 / 3 / 4 Answer 0 / 1 / 2 ________pts / 6 pts 7. Carbon dioxide (CO2) and bicarbonate (HCO3−) concentrations in the bloodstream are physiologically controlled to keep blood pH constant at a normal value of 7.40. Physicians use the following modified form of the Henderson-Hasselbach equation to track changes in blood pH: ࠵?࠵? = ࠵?࠵?࠵? + log *[࠵?࠵?࠵?3 −]0.030 ∗ ࠵?࠵?࠵?26where [HCO3−] is given in millimoles/liter and the arterial blood partial pressure of CO2(PCO2) is given in mmHg. The pKa of carbonic acid is 6.1. Hyperventilation causes a physiological state in which the concentration of CO2in the bloodstream drops. The drop in the partial pressure of CO2constricts arteries and reduces blood flow to the brain, causing dizziness or even fainting. If the normal physiological concentration of HCO3−is 24 mM, what is the pH of blood if PCO2drops to 31.0 mmHg? Express your answer numerically using two decimal places. Page 2 ________ pts / 8 pts Page 3 ________ pts / 10 pts Page 4 ________ pts / 10 pts Page 5 ________ pts / 10 pts Page 6 ________ pts / 6 pts Page 7 ________ pts / 6 pts TOTAL ________ pts / 50 pts Graded by TA: _____________
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- Fall '19
- pH, buffer solution