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y Bookmarks Window Help saplinglearning.com Solutions and Study Help Chegg.com University of South Florida CHM 20 3/30/2016 11:30 PM O 92.9/1003/30/2016 10:57 PM Print Calculator Periodic Table · Question 2 of 14 Maj You have 175 mL of an 0.53 M acetic acid solution. What volume (V) of 1.40 M NaOH solution must you add in order to prepare an acetate buffer of pH = 4.817 (The pK of acetic acid is 4.76) Number mL NaOH Previous Give Up & View Solution ( Check Answer Next Ext about us careers partners privacy policy terms of use contact us 30Explanation / Answer
CH3COOH + NaOH ------> CH3COONa +H2O
Mole ratio is 1:1
pH of buffer can be determined by Henderson equation;
pH= pKa+ log (CH3COO-)/(CH3COOH)
4.81= 4.76 + log (CH3COO-)/(CH3COOH)
log (CH3COO-)/(CH3COOH)= 4.81-4.76= 0.05
(CH3COO-)/(CH3COOH)= 10^0.05= 1.12
CH3COO-= 1.12 CH3COOH...... (1)
Volume of acetic acid=175ML=0.175 L
Moles of acetic acid= 0.175* 0.53=0.093
So, CH3COOH +CH3COO-= 0.093moles...(2)
Plug in the value from equation 1 in 2;
CH3COOH+ 1.12 CH3COOH= 0.093
CH3COOH= 0.093/2.12= 0.043 moles
CH3COO- = 0.093-0.043=0.05 moles
NaOH is a strong base and will deprotanate CH3COOh to give CH3COO-, so 0.05moles of NaOH are needed.
Volume of NaOH= moles/molarity= 0.05/1.40= 0.035 L or 35 ml
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