The \(K_a\) values of A, B and C are \(1.8\times 10^{-4}\), \(5\times 10^{-10}\) and \(3\times 10^{-8}\) respectively. The correct order of their acidic strength is
Show Hint
Acidic strength is directly proportional to the acid dissociation constant:
\[
\text{Higher }K_a \Rightarrow \text{stronger acid}
\]
So, compare \(K_a\) values directly to arrange acidic strength.
Step 1: Understand the relation between \(K_a\) and acidic strength.
The acid dissociation constant is represented by
\[
K_a
\]
A higher value of
\[
K_a
\]
means the acid dissociates more in water.
Therefore, greater \(K_a\) means greater acidic strength.
Step 2: Write the given \(K_a\) values.
For acid A,
\[
K_a=1.8\times 10^{-4}
\]
For acid B,
\[
K_a=5\times 10^{-10}
\]
For acid C,
\[
K_a=3\times 10^{-8}
\]
Step 3: Compare the \(K_a\) values.
Now compare the powers of \(10\):
\[
10^{-4} \gt 10^{-8} \gt 10^{-10}
\]
Thus,
\[
1.8\times 10^{-4} \gt 3\times 10^{-8} \gt 5\times 10^{-10}
\]
Therefore,
\[
K_a(A)\gt K_a(C)\gt K_a(B)
\]
Step 4: Arrange the acidic strengths.
Since acidic strength is directly proportional to \(K_a\),
\[
\text{Acidic strength order}=A\gt C\gt B
\]
Step 5: Final conclusion.
Hence, the correct order of acidic strength is
\[
\boxed{A\gt C\gt B}
\]
