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PRE-LABORATORY QUESTIONS EXPERIMENT 5 1. A student is asked to prepare 200. mL of a 0.10 M buffer with pH = 8.30. There are two weak acids the student can choose from. Acid A has a pK a of 10.50 and Acid B has a pK a of 7.50. Which acid should the student pick? Briefly explain your choice. pH ranges: 11.50-9.50 for Acid A 8.50-6.50 for Acid B The best choice would be Acid B since the desired pH is in the range based on the pK a . 2. How many grams of the conjugate base of molar mass 175 g/mol will have to be added to a solution of a weak acid to make 200. mL of a buffer in which the concentrations of the weak acid and its conjugate base are each 0.200 M? (0.200 mole/L) (0.200 L) = X g of the conjugate base/175 g/mole X = 7.00 grams of the conjugate base 3. Write the hydration reaction and the hydrolysis reaction for sodium nitrite, NaNO 2 . Will the pH of the solution be acidic, neutral or basic? Hydration:

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