i/ibis/view.php?.( -Course Home Cuyahoga Commu.. xClassity Eac CHEM 1310-Spring1

Question

i/ibis/view.php?.( -Course Home Cuyahoga Commu.. xClassity Eac CHEM 1310-Spring16- MIGYANKO Actvities and Due Dates HW19a 2016 12:00 AM 81/100 Print CalculatorPeriodic Table n 8 of 21 ng Buffer capacity is a measure of a buffer solution's resistance to changes in pH as strong acid or base is added. Suppose that you have 145 mL of a buffer that is 0.240 M in both benzoic acid (CetCOOH) and its t is 0.240 M in both benzoic acid (CoHsCOOH) and its conjugate base (CsHsCOO) Calculate the maximum volume of 0.370 M HCI that can be added to the buffer before its buffering capacity is lost. Number 94.05 mL There is a hint availablel Vew the hint bottom divider on the on the divider bar again to hide the hint Close O Prevous Give Up & View Solution Check Answer Next Exit about us careers partners privacy poncy terms o

Explanation / Answer

buffer capacity may be pka +/- 1

addition of HCl decreases pH , that can be observed maximum up to pka - 1

pka of benzoicacid = 4.2

if pH = pka capacity is maximum

4.2 = 4.2 + log(salt/acid)

No of mol of buffer = 0.145*0.24 = 0.0348 mol

4.2 = 4.2 + log(x/(0.0348-x))

x = 0.0174 mol = no of mol of conjugate base

no of mol of benzoicacid = 0.0348 - 0.0174 = 0.0174 mol

pH = 4.2-1 = 3.2

pH = pka + log(

3.2 = 4.2 + log((0.0174-x)/( 0.0174+x))

x = No of mol of HCl added = 0.0142 mol

Volume of HCl = 0.0142/0.37 = 0.0387 L

= 38.7 ml

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