Which of the following mixtures will be a buffer when dissolved in a liter of water?
a. 0.1 mol Ca(OH)2 and 0.3 mol HI
b. 0.3 mol NaCl and 0.3 mol HCl
c. 0.4 mol NH3 and 0.4 mol HCl
d. 0.2 mol HBr and 0.1 mol NaOH
e. 0.2 mol H3PO4 and 0.1 mol NaOH
i think e is answer but not sure.
A buffer is one containing a weak acid and its salt or a weak base and its salt. I think e also, NaOH added to H3PO4 forms NaH2PO4 and there is some H3PO4 left over.
To determine which mixture will be a buffer when dissolved in a liter of water, we need to consider the components of a buffer solution. A buffer solution consists of a weak acid and its conjugate base or a weak base and its conjugate acid.
Let's analyze each option:
a. 0.1 mol Ca(OH)2 and 0.3 mol HI
- Ca(OH)2 is a strong base, and HI is a strong acid. This combination does not form a buffer.
b. 0.3 mol NaCl and 0.3 mol HCl
- NaCl is a strong salt, and HCl is a strong acid. This combination does not form a buffer.
c. 0.4 mol NH3 and 0.4 mol HCl
- NH3 is a weak base, and HCl is a strong acid. This combination can form a buffer since it contains a weak base and its conjugate acid. It is a potential answer.
d. 0.2 mol HBr and 0.1 mol NaOH
- HBr is a strong acid, and NaOH is a strong base. This combination does not form a buffer.
e. 0.2 mol H3PO4 and 0.1 mol NaOH
- H3PO4 is a weak acid, and NaOH is a strong base. This combination can form a buffer since it contains a weak acid and its conjugate base. It is also a potential answer.
Based on the analysis, both options c and e have the potential to form a buffer when dissolved in water. However, to determine the exact answer, we need to compare their acidic and basic strengths.
The acidity constant (Ka) for H3PO4 is larger than the Ka for NH3, so option e (0.2 mol H3PO4 and 0.1 mol NaOH) is a stronger choice for a buffer solution.
Therefore, the correct answer is e. 0.2 mol H3PO4 and 0.1 mol NaOH.
To determine which mixture will act as a buffer when dissolved in water, we need to understand what a buffer is and how it is formed.
A buffer is a solution that resists changes in pH when small amounts of acid or base are added to it. It is typically composed of a weak acid and its conjugate base, or a weak base and its conjugate acid.
To identify a buffer, we need to find a pair of substances within the mixture that can act as a weak acid and its conjugate base, or a weak base and its conjugate acid.
Now, let's analyze each option:
a. 0.1 mol Ca(OH)2 and 0.3 mol HI:
Ca(OH)2 is a strong base, and HI is a strong acid. Therefore, this mixture does not have a weak acid and its conjugate base, or a weak base and its conjugate acid. It is not a buffer.
b. 0.3 mol NaCl and 0.3 mol HCl:
Both NaCl and HCl are strong acids and do not have corresponding weak acid-base pairs. This mixture is not a buffer.
c. 0.4 mol NH3 and 0.4 mol HCl:
NH3 is a weak base, and HCl is a strong acid. This mixture contains both a weak base (NH3) and its conjugate acid (NH4Cl). It can act as a buffer.
d. 0.2 mol HBr and 0.1 mol NaOH:
HBr is a strong acid, and NaOH is a strong base. This mixture does not have a weak acid and its conjugate base, or a weak base and its conjugate acid. It is not a buffer.
e. 0.2 mol H3PO4 and 0.1 mol NaOH:
H3PO4 is a weak acid, and NaOH is a strong base. This mixture contains both a weak acid (H3PO4) and its conjugate base (H2PO4-). It can act as a buffer.
Therefore, the correct answer is option e. 0.2 mol H3PO4 and 0.1 mol NaOH.