0
answers
0
watching
185
views
17 Nov 2019
More buffer practice! The following sequence of questions is intended to give you more practice with buffer calculations, particularly the pre-lab questions. for Experiment 3. Useful equations... Hendersen-Hasselbach: pH = pKa + log([A-]/[HA]) Concentration (molarity): molarity = moles solute/VoL Solution (in liters) A student wants to prepare 90.0 mL of a 0.225 M buffer with a final pH of 7.2, using the buffer EPPS (MW = 252.332 g/mol: pKa = 8.0) How many grams of solid EPPS must be weighed out? Determine the value of [A-]/[HA] using the desired pH(7.2) and pKa of EPPS. EPPS is an acidic buffer. NaOH must be added to convert the acid form of EPPS (HA) to its conjugate base (A-), we can calculate the concentration of NaOH necessary to achieve the desired ratio of [A-]/[HA] calculated in Q.6 using the following equation: [A-]/[HA] = x/(Cone - x): where Cene. = final buffer concentration (0.225 M) Solve for x. The unknown x is in units of molarity (moles/liter). Using the desired volume(90.0 mL), how many moles of NaOH would this be? How many mL of 1 M NaOH would be required to deliver the moles calculated in Q.8?
More buffer practice! The following sequence of questions is intended to give you more practice with buffer calculations, particularly the pre-lab questions. for Experiment 3. Useful equations... Hendersen-Hasselbach: pH = pKa + log([A-]/[HA]) Concentration (molarity): molarity = moles solute/VoL Solution (in liters) A student wants to prepare 90.0 mL of a 0.225 M buffer with a final pH of 7.2, using the buffer EPPS (MW = 252.332 g/mol: pKa = 8.0) How many grams of solid EPPS must be weighed out? Determine the value of [A-]/[HA] using the desired pH(7.2) and pKa of EPPS. EPPS is an acidic buffer. NaOH must be added to convert the acid form of EPPS (HA) to its conjugate base (A-), we can calculate the concentration of NaOH necessary to achieve the desired ratio of [A-]/[HA] calculated in Q.6 using the following equation: [A-]/[HA] = x/(Cone - x): where Cene. = final buffer concentration (0.225 M) Solve for x. The unknown x is in units of molarity (moles/liter). Using the desired volume(90.0 mL), how many moles of NaOH would this be? How many mL of 1 M NaOH would be required to deliver the moles calculated in Q.8?