Ka values of some compound are given below, select the correct order of acidic strength:i.H2O ⇌H++OH-Ka=1 x 10^-14 ii. ROH⇌RO-+H+Ka=1 x 10^-18 iii. RCOOH⇌RCOO-+H+Ka=1 x 10^-5 iv.C6H5OH⇌C6H5O-+ H+Ka=1 x 10^-10
Correct answer: C. RCOOH > C6H5OH > H2O > ROH
- A. ROH> H2O> C6H5OH>RCOOH
- B. C6H5OH > H2O> ROH > RCOOH
- C. RCOOH > C6H5OH > H2O > ROH
- D. RCOOH > ROH > C6H5OH > H2O
Explanation
The increasing strength of acidities is as follows; carboxylic acids, phenols, water and then ethanol. Students should know that carboxylic acids have two electronegative atoms which make the carboxylate anion stable whereas ethanol has positive inductive effect due to the presence of alkyl groups so it is the least acidic. This order is only followed by option C which is the answer
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About Bronsted-Lowry and Lewis Concepts
The Brønsted-Lowry concept defines acids as proton donors and bases as proton acceptors, producing conjugate acid-base pairs. The Lewis concept extends the idea to electron-pair acceptors and donors, so compounds such as BF3 and NH3 can be treated as acid and base even without proton transfer, unlike the Arrhenius definition.
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