Can someone please please help me I understand the problem solving part of the equation, what I want to know is when do
Posted: Thu Jul 07, 2022 1:47 pm
Can someone please please help me
I understand the problem solving part of the equation, what I want to know is when do you know when to use pH - pKa and when do you use pKa-pH?Because if the value is pKa is smaller than pH it gives you a negative then they turn the equation of log(A-/HA) around to (HA/A-)
27. Preparation of Buffer of Known pH and Strength Given 0.10 M solutions of acetic acid (pK₁ = 4.76) and sodium acetate, describe how you would go about preparing 1.0 L of 0.10 M acetate buffer of pH 4.00. Answer Use the Henderson-Hasselbalch equation to calculate the ratio [Ac /[HAc] in the final buffer. pH=pK₂ + log ([Ac V[HAC]) log ([Ac 1/[HAc]) = pH - pK₂ = 4.00 4.76 = -0.76 [Ac V[HAC] = 10-0.76 A-/HA= antilog -0.76 HA/A-=antilog +0.76 HA/A-= 5.75 HA/A- = 5.75/1 HA=5.75/6.75 = 0.85 A = 1/6.75 = 0.15 The fraction of the solution that is Ac = [Ac /[HAC + Ac] = 10-0.76/(1+ 10-0.76) = 0.148, which must be rounded to 0.15 (two significant figures). Therefore, to make 1.0 L of acetate buffer, use 150 mL of sodium acetate and 850 mL of acetic acid.
- Can Someone Please Please Help Me I Understand The Problem Solving Part Of The Equation What I Want To Know Is When Do 1 (153.06 KiB) Viewed 52 times
27. Preparation of Buffer of Known pH and Strength Given 0.10 M solutions of acetic acid (pK₁ = 4.76) and sodium acetate, describe how you would go about preparing 1.0 L of 0.10 M acetate buffer of pH 4.00. Answer Use the Henderson-Hasselbalch equation to calculate the ratio [Ac /[HAc] in the final buffer. pH=pK₂ + log ([Ac V[HAC]) log ([Ac 1/[HAc]) = pH - pK₂ = 4.00 4.76 = -0.76 [Ac V[HAC] = 10-0.76 A-/HA= antilog -0.76 HA/A-=antilog +0.76 HA/A-= 5.75 HA/A- = 5.75/1 HA=5.75/6.75 = 0.85 A = 1/6.75 = 0.15 The fraction of the solution that is Ac = [Ac /[HAC + Ac] = 10-0.76/(1+ 10-0.76) = 0.148, which must be rounded to 0.15 (two significant figures). Therefore, to make 1.0 L of acetate buffer, use 150 mL of sodium acetate and 850 mL of acetic acid.