Ethylene has a pKa value of 25, water has a pKa value of 15.7, and ammonia (NH3)

Question

Ethylene has a pKa value of 25, water has a pKa value of 15.7, and ammonia (NH3) has a pKa value of 36.

0 ,dI33) 11:05 p.m. asteringchemistry.com D Problem 2 2 of 18 Ethyne has a pKa value of 25, water has a pKa value of 15.7, and ammonia (NHs) has a pK, value of 36. Part A Write the equation in the direction, which favors the equilibrium, for the acid-base reaction of ethyne with HO Express your answer as an acid-base reaction. In case the reaction favors towards reactants re- write an equation in the reverse direction. HC CH+HO HC CH20 Submit Request Answer Incorrect; Try Again; 8 attempts remaining Part B Write the equation in the direction, which favors the equilibrium, for the acid-base reaction of ethyne with (NH2) Express your answer as an acid-base reaction. To write an ion show it in brackets and a charge after it (NH 2)A-. In case the reaction favors towards reactants re-write an equation in the reverse direction. SubmitRequest Answer Part C Part complete Which would be a better base to use if you wanted to remove a proton from ethyne? HO Submit Correct Next

Explanation / Answer

We know that pKa is inversely proportional to acidity

From pKa values, the acidity of Ethylene, water, and NH3 is in the order of

H2O > Ethylene > NH3

basicity order of their conjugate bases is in the order of

OH- < Ethylidene ion < NH2-

Part 1: H2C=CH2 + OH- ===== H2C=CH- + H2O

Since H2C=CH- is more basic than OH-, thus the equilibrium lies towards left side i.e., reactants side

Part 2: H2C=CH2 + NH2- ===== H2C=CH- + NH3

Since NH2- is more basic than H2C=CH-, thus the equilibrium lies towards right side i.e., products side

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