Chemistry Question How many grams of KOH?

How many grams of KOH must be added to 0.500 L of the buffer to change the pH by 0.150 units?



GIVEN:



A buffer is prepared by mixing 206mL of 0.452 M HCl and 0.500 L of 0.400 M sodium acetate and the pH is 4.805.Chemistry Question How many grams of KOH?
moles HCl = 0.206 L x 0.452 M= 0.0931

moles acetate = 0.500 x 0.400=0.200



CH3COO- + H+ = CH3COOH

moles acetate = 0.200 - 0.0931=0.107

moles acetic acid = 0.0931

total volume = 0.706 L



[acetate]= 0.107 / 0.706 =0.151 M

[acetic acid ]= 0.0931/ 0.706=0.132 M



4.805 = pKa + log 0.151/0.132

pKa = 4.75



moles acetic acid in 0.500 L = 0.132 x 0.500=0.0660

moles acetate in 0.500 L = 0.151 x 0.500 =0.0755



pH must be 4.805 + 0.150= 4.955



4.955 - 4.75 =0.205

10^0.205 =1.60 = ln [acetate]/ [acetic acid]



1.60 = 0.0755+x / 0.0660-x



0.105 - 1.60 x = 0.0755+x

0.105 - 0.0755 = 2.60 x

x = 0.00397



mass KOH = 0.00397 x 56.107 g/mol=0.223 g