This set of Bioprocess Engineering Multiple Choice Questions & Answers (MCQs) focuses on “Buffers”.
1. The pH of the solution is directly proportional to the carbonate concentration when added to the solution.
a) True
b) False
View Answer
Explanation: Many media are buffered at about pH 7.0 by the incorporation of calcium carbonate. If the pH decreases the carbonate is decomposed.
2. If a drop of decinormal HCI is added to a mixture of weak acid and its strong salt then in the following condition which option is correct?
a) Very high change in H+ ions
b) High change in H+ ions
c) Slight change in H+ ions
d) No change in H+ ions
View Answer
Explanation: When a drop of decinormal HCL is added to a mixture of weak acid and its strong salt (e. g. , CH3COOH + CH3COONa) there is a very slight change of H+ ion concentration. It means the pH value in these media remains approximately the same and these solutions resist any change of acidity or alkalinity.
3. If a decinormal solution of NaOH is added in a mixture of weak base and its strong salt then in the following condition which option is correct?
a) Very high change in OH– ions
b) High change in OH– ions
c) Slight change in OH– ions
d) No change in OH– ions
View Answer
Explanation: When a decinormal solution of NaOH is added in a mixture of weak base and its strong salt (e. g.,NH4OH + NH4Cl) then a slight change in OH ion concentration takes place. It means the pH value in these media remains approximately the same and these solutions resist any change of acidity or alkalinity.
4. Which of the following is not a simple buffer?
a) CH3COONH4
b) NH4CN
c) H3PO4 + NaH2PO4
d) (NH4)2 CO3
View Answer
Explanation: H3PO4 + NaH2PO4 is a type of mixed buffer of acidic buffer mixture which is combination of a weak acid with its salt of strong base.
5. Which of the following is not a type of Acidic buffer mixture?
a) Na2HPO4 + Na3PO4
b) CH3COOH+ CH3COONa
c) H2CO3+Na2CO3
d) H3PO4+NaH2PO4
View Answer
Explanation: Na2HPO4 + Na3PO4 is a type of simple buffer which is a combination of a mixture of an acid salt and normal salt of a poly basic acid.
6. Which of the following is not a type of Basic buffer mixture?
a) NH4OH
b) NH4Cl
c) H2CO3+Na2CO3
d) Glycine + Glycine hydrochloride
View Answer
Explanation: H2CO3+Na2CO3 is a type of mixed buffer of acidic buffer mixture which is combination of a weak acid with its salt of strong base.
7. What is the molecular weight of water?
a) 10 g/mol
b) 20 g/mol
c) 8 g/mol
d) 18 g/mol
View Answer
Explanation: The molecular weight of water is 18.015 g/mol.
8. What is the H+ ion concentration in pure water?
a) 1×107 m
b) 1×10-7 m
c) 1×1014 m
d) 1×10-14 m
View Answer
Explanation: The character of acidic, basic and neutral is defined by the concentration of hydrogen ions [H+](mol/L). A solution with a concentration of hydrogen ions higher than 10-7mol/L is acidic, and a solution with a lower concentration is alkaline (another way to say basic).
9. In one liter of water how many moles of water are present?
a) 25 moles
b) 30 moles
c) 50 moles
d) 55 moles
View Answer
Explanation: The reaction does not form very much H3O+ or OH–. In one liter of water there are about 55 moles of water molecules, but only 1.0 x 10-7moles of H3O+ and OH– are formed (at room temperature).
10. The pH of buffer solution depends upon concentration of?
a) Strong acid
b) Strong base
c) Weak acid
d) Salt
View Answer
Explanation: A buffer solution (more precisely, pH buffer or hydrogen ion buffer) is an aqueous solution consisting of a mixture of a weak acid and its conjugate base, or vice versa.
11. The pH is directly proportional to pKa?
a) True
b) False
View Answer
Explanation: The buffer capacity depends essentially on 2 factors: Ratio of the salt to the acid or base. The buffer capacity is optimal when the ratio is 1:1; that is, when pH = pKa. Total buffer concentration.
12. The pH can be kept constant with the help of?
a) Saturated solution
b) Unsaturated solution
c) Buffer solution
d) Non-Saturated solution
View Answer
Explanation: A buffer is a special solution that stops massive changes in pH levels. Every buffer that is made has a certain buffer capacity, and buffer range. The buffer capacity is the amount of acid or base that can be added before the pH begins to change significantly. It can be also defined as the quantity of strong acid or base that must be added to change the pH of one liter of solution by one pH unit. The buffer range is the pH range where a buffer effectively neutralizes added acids and bases, while maintaining a relatively constant pH.
13. A solution was prepared by dissolving 0.02 moles of acetic acid (HOAc; pKa = 4.8) in water to give 1 liter of solution. What is the pH?
a) 3.00
b) 3.05
c) 3.15
d) 3.25
View Answer
Explanation:
14. A solution of acetic acid (HOAc) was prepared by dissolving 0.02 moles of acetic acid in water to give 1 liter of solution. If 0.008 moles of sodium hydroxide (NaOH) are added to this solution, what is the new pH?
a) 4.00
b) 4.53
c) 4.63
d) 4.50
View Answer
Explanation: NaOH is a strong base. It will react nearly quantitatively with HOAc to produce OAc-.
15. After the addition of 0.008 moles of sodium hydroxide (NaOH) to the solution of acetic acid (HOAc), an additional 0.012 moles of NaOH is added. What is the pH of the solution now?
a) 8.44
b) 8.40
c) 8.54
d) 8.50
View Answer
Explanation: After the addition of another 0.012 moles of NaOH, all of the HOAc has been converted to NaOAc. thus, [OAc-] = 0.02 M. Since only the “base form” of the HOAc is now present,
Sanfoundry Global Education & Learning Series – Bioprocess Engineering.
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