You are preparing a sample for Kjeldahl analysis. Based on the protein information in the sample, you need to use a buffer with pH=8. Which of the following weak base and its conjugate acid will you use?
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You are preparing a sample for Kjeldahl analysis. Based on the protein information in the sample, you need to use a buffer with pH=8. Which of the following weak base and its conjugate acid will you use?
a. NH2OH, pKb = 8.04
b. CH3CH2NH2, pKb = 3.37
c. NaH2PO4, pKa = 7.21
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- 2. Joey was tasked to ensure that an enzyme responsible for keeping his species from extinction remains biologically active. To do so, he needs to store it in a buffer solution with a pH of 10.00. Unfortunately, only three buffer systems are available in their laboratory: Buffer System Weak Acid Component Ka Conjugate Base Salt KYA Benzoic acid, C6H5COOH 6.25 x 105 NaCH₂COO MUH Boric acid, H3BO3 5.81 x 107 NaH₂BO TWO Hydrogen cyanide, HCN 6.20 X 10-10 NaCN A. In what buffer system (KYA, MUH, or TWO) will Joey store the enzyme? In your solution sheet, show calculations and briefly explain to support your answer. B. Write the equilibrium reaction involved in the buffer system. Write your answer on your solution sheet C. Calculate the amount (in mL) of the 1.75 M stock solution (pH 7.00) of the same buffer system needed to prepare 250 mL of a 0.550 M buffer pH 7.00. After preparing the buffer, Joey decided to determine the buffer capacity of the solution by titration using 0.500 M NaOH as…You are given 0.7 M solution of the amino acid Lysine. pK1 (α-carboxyl group) = 2.18 pK2 (α- amino group) = 8.95 and pK3 (Side chain) = 10.53 Answer the following questions. a. Determine the pH of the solution if you add 26 mL 0.3 M HCl to 12 mL of the 0.7 M Lysine. Assume that Lysine is in isotonic state. Show all calculations. b. Draw the structure of the amino acid at the pH determined in question aYou have 0.500 L of an 0.250 M acetate buffer solution (i.e. [HC2H3O2] + [C2H;O2] = 0.250 M) at pH 3.50. How many mL of 1.000 M NaOH must you add in order to change the pH to 5.37? Acetic acid has a pka of 4.74. mL 1 2 3 4 C 7 8 9. +/- х 100 +
- You need to prepare 100.0 mL of a pH 4.00 buffer solution using 0.100 M benzoic acid (pK₁ = 4.20) and 0.200 M sodium benzoate. How many milliliters of each solution should be mixed to prepare this buffer? benzoic acid: sodium benzoate: mL mL1. biology. The reagent of CHES is N-cyclohexyl-2-aminoethanesulfonic acid, a monoprotic acid, with a formula of CSH17NO:S. It has a useful pH range between 8.6 to 10. It is made by reacting with NaOH in situ. How many grams of solid CHES should be added to 100.0 mL of 0.500 M NaOH to make a buffer of pH = 9.54? Ka for CHES is 5.0 × 1010. Please note NaOH is used to make the CHES salt, and not part of HH equation. CHES buffer is a commonly used buffer system in biochemistry and molecular4. You need to make a buffer with pH as close to 10.00 as possible. Two sets of weak acids and conjugate bases, with the Ka values, are listed below. Which of the two sets would be the best choice? You want a pka close to the pH. Explain your reasoning. CH:COOH/CH;coo HCO; /CO,2- Ka = 1.80 x 10s Ka = 2.14 x 10-10 %3D %3D 5. 5 drops of a strong base (0.1 M concentration) was added to a buffer (pH = 7.0), with no apparent change in pH. An additional 5 ml of this strong base was added, and the pH of the solution increased to 13.0. Explain why there was no apparent change in pH in the %3D first case, but a marked change in pH in the second case.
- You need to prepare 100.0 mL of a pH 4.00 buffer solution using 0.100 M benzoic acid (pK₁ = 4.20) and 0.200 M sodium benzoate. How many milliliters of each solution should be mixed to prepare this buffer? benzoic acid: 25.96 Incorrect sodium benzoate: 74.04 Incorrect mL mLYou have 0.500 L of an 0.250 M acetate buffer solution (i.e. [HC₂H₃O₂] + [C₂H₃O₂⁻] = 0.250 M) at pH 3.50. How many mL of 1.000 M NaOH must you add in order to change the pH to 4.98? Acetic acid has a pKa of 4.74.A chemist needs to buffer a particular solution between pH 3.50 and 4.00 at 25 °C. Consider the pKą values (all at 25 °C) and determine which solution is most appropriate for the task. HCIO pK₂ = 1.96 C6H5CO₂H pK₂ = 4.19 C5HẠNH* pK₂ = 5.25 HBrO pK₂ = 8.70 HCN pK₂ = 9.21 C6H5CO₂H and KC6H5CO2 C5H4NHCI and C5H4N HBrO and KBRO HCIO and NaCIO HCN and NaCN
- You are asked to make a buffer of pH 3.4 and given the above acids. Of these acids, which would create a buffer with the best capacity against acids? Which would have the best buffering capacity against bases? Which could not be used at all for this project? Best against acids Best against bases Acid #1 has a pka of 3.15 Acid #2 has a pKa of 3.65 Acid #3 has a pKa of 4.23 Acid #4 has a pka of 4.79 Cannot be used Acid #2 Acid #1 Acid #4Given the Kb's of three weak bases and the Ka's of two weak acids choose the one that could be used as one of the components of a buffer solution with a pH of 6.35. 1. CH3COOH (Ka = 1.8 x 10–5) 2. NH2OH (Kb = 1.1 x 10–8) 3. CH3NH2 (Kb = 4.4 x 10–4) 4. C5H5N (Kb = 1.7 x 10–9) 5. HCOOH (Ka = 1.8 x 10–4)+ Base/Acid Ratios in Buffers Just as pH is the negative logarithm of [H3O+]. PK₁ is the negative logarithm of Ka. PK₂ = -log Ka The Henderson-Hasselbalch equation is used to calculate the pH of buffer solutions: pH=pK₁ +log base [acid] Notice that the pH of a buffer has a value close to the PK₂ of the acid, differing only by the logarithm of the concentration ratio [base]/[acid]. The Henderson-Hasselbalch equation in terms of pOH and PKb is similar. lacid] pOH = pk + logad base pH 3.74 [acetic acid] ten times greater than [acetate] Submit ✓ Correct ▼ Part B pH = 4.74 Previous Answers [acetate] = [acetic acid] mass of NH4Cl = pH = 5.74 [acetate] ten times greater than [acetic acid] Value How many grams of dry NH4Cl need to be added to 2.00 L of a 0.100 M solution of ammonia, NH3. to prepare a buffer solution that has a pH of 8.85? Kb for ammonia is 1.8 x 10-5 Express your answer with the appropriate units. ▸ View Available Hint(s) ( 2 F Templates Symbols undo relo reset keyboard…
