Rank the following solutions in order based on pH. (1 = Highest pH; 4 = Lowest pH)
$0.1 M HC _2 Cl _3 O _2$
[ Choose ]
$0.1 M KClO _4$
[ Choose ]
$0.1 M NaClO _2$
[ Choose ]
0.1 M NaF
[ Choose ]
Answer (2)
Identify the nature of each solution: acid ( H C 2 C l 3 O 2 ), neutral ( K Cl O 4 ), and basic ( N a Cl O 2 and N a F ).
Compare the basicity of N a Cl O 2 and N a F by comparing the K a values of their conjugate acids ( H Cl O 2 and H F ).
Since H F is a weaker acid than H Cl O 2 , N a F is more basic than N a Cl O 2 .
Rank the solutions from highest pH to lowest pH: NaF > KClO_4 > HC_2Cl_3O_2}"> N a Cl O 2 > N a F > K Cl O 4 > H C 2 C l 3 O 2
Explanation
Problem Analysis We are given four solutions: 0.1 M H C 2 C l 3 O 2 , 0.1 M K Cl O 4 , 0.1 M N a Cl O 2 , and 0.1 M N a F . We need to rank these solutions based on their pH, with 1 being the highest pH and 4 being the lowest pH.
Identifying Acidic, Basic, and Neutral Solutions First, let's identify the nature of each solution. H C 2 C l 3 O 2 (trichloroacetic acid) is a weak acid. K Cl O 4 is a salt formed from a strong acid ( H Cl O 4 ) and a strong base ( K O H ), so it's a neutral solution. N a Cl O 2 is a salt formed from a weak acid ( H Cl O 2 ) and a strong base ( N a O H ), so it's a basic solution. N a F is a salt formed from a weak acid ( H F ) and a strong base ( N a O H ), so it's also a basic solution.
Comparing Basicity of Salts Now, let's compare the basicity of N a Cl O 2 and N a F . The strength of a base is related to the weakness of its conjugate acid. The weaker the conjugate acid, the stronger the base. The K a of H Cl O 2 is approximately 0.011 , and the K a of H F is approximately 0.00068 . Since H F is a weaker acid than H Cl O 2 , F − is a stronger base than Cl O 2 − . Therefore, N a F is more basic than N a Cl O 2 .
Ranking the Solutions Based on the above analysis, we can rank the solutions from highest pH (most basic) to lowest pH (most acidic): NaF > KClO_4 > HC_2Cl_3O_2"> N a Cl O 2 > N a F > K Cl O 4 > H C 2 C l 3 O 2 . Therefore, the ranking is:
N a Cl O 2
N a F
K Cl O 4
H C 2 C l 3 O 2
Examples
Understanding pH ranking is crucial in various real-life applications. For example, in agriculture, knowing the pH of the soil helps farmers choose the right crops and fertilizers. Similarly, in medicine, maintaining the correct pH balance in the body is essential for various biological processes. In environmental science, monitoring the pH of water bodies helps assess pollution levels and protect aquatic life. This ranking exercise provides a foundation for understanding and addressing pH-related issues in these diverse fields.
The solutions ranked by pH from highest to lowest are: 1. N a F , 2. N a Cl O 2 , 3. K Cl O 4 , and 4. H C 2 C l 3 O 2 . N a F is the strongest base, while H C 2 C l 3 O 2 is the weakest, being a weak acid. Neutral salts like K Cl O 4 fall in the middle.
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