Select only the True statements about buffer systems.
Select all that are True.
1. Starting with NH3(aq) and adding a small amount of HCl(aq) will make a buffered solution.
2. The blood buffer, among other things, is supported by carbonic acid and its conjugate base bicarbonate.
3. If a buffer is made from a weak acid and its conjugate base, it will have a pH<7.0.
4. Mixing amounts of NaOH and HCl will make a buffer with a pH=7.0.
5. A mixture of similar amounts of NaH2PO4 and Na2HPO4 in an aqueous solution would have a pH around 7.2.
6. Making a solution of H2SO4(aq) and HSO4−(aq) is an ideal buffer.
7. A mixture of similar amounts of HCO3- and CO32- in an aqueous solution would have a pH around 6.4.
I have tried 7 times
This is a little confusing to me; i.e., #1 will make a buffer but not a very good one. #4 will have a pH = 7.0 but not good buffering characteristics.
I need to know what you don't understand and what have you answered (and why?)
To determine which statements are true about buffer systems, let's analyze each option:
1. Starting with NH3(aq) and adding a small amount of HCl(aq) will make a buffered solution.
This statement is false. A buffered solution requires a weak acid and its conjugate base, not an acid (HCl) and a base (NH3).
2. The blood buffer, among other things, is supported by carbonic acid and its conjugate base bicarbonate.
This statement is true. The blood buffer system relies on the equilibrium between carbonic acid (H2CO3) and bicarbonate (HCO3-).
3. If a buffer is made from a weak acid and its conjugate base, it will have a pH<7.0.
This statement is false. A buffer made from a weak acid and its conjugate base can have a pH greater than, equal to, or less than 7.0 depending on the specific acid and base involved.
4. Mixing amounts of NaOH and HCl will make a buffer with a pH=7.0.
This statement is false. Mixing equal amounts of a strong base (NaOH) and a strong acid (HCl) will result in a neutral solution with a pH of 7.0, but it is not considered a buffered solution.
5. A mixture of similar amounts of NaH2PO4 and Na2HPO4 in an aqueous solution would have a pH around 7.2.
This statement is false. The pH of a buffer solution depends on the pKa of the weak acid involved. Without specific information regarding the pKa values of NaH2PO4 and Na2HPO4, we cannot determine the pH.
6. Making a solution of H2SO4(aq) and HSO4−(aq) is an ideal buffer.
This statement is false. H2SO4 (sulfuric acid) is a strong acid, and HSO4- (bisulfate) is its conjugate base. A buffer requires a weak acid and its conjugate base, so H2SO4 and HSO4- do not form an ideal buffer system.
7. A mixture of similar amounts of HCO3- and CO32- in an aqueous solution would have a pH around 6.4.
This statement is false. HCO3- (bicarbonate) and CO32- (carbonate) represent a basic buffer system, but their exact pH value depends on the concentrations and the pKa value of carbonic acid, H2CO3. Without specific information, we cannot determine the precise pH.
Based on this analysis, the only true statement about buffer systems is statement 2: "The blood buffer, among other things, is supported by carbonic acid and its conjugate base bicarbonate."