Question

Which one of the following options is correct?

• A. Greater the $K_a$ value, greater is the acidic strength
  
• B. Greater the $p{K}_a$ value, greater the acidic strength
• C. Smaller the $pH$ value, greater the acidic strength. (Comparing same concentration of acids)
• D. (a) and (c) above.

Answer 1

The correct option is D (a) and (c) above.

More acidic the compound larger its $K_a$ value. larger the $K_a$ value and smaller its $p{K}_a$.(as $p{K}_a=-log{K}_a$)
Also $pH=-log\left[H^{+}\right]$ Therefore more acidic the compound more the $H^{+}$ ion concentration and lower the pH value.