# Arrange the following in increasing order of acidity: water, ammonia, ethyne and ethane

I know that ethyne is more acidic than ethane because of more s character. For water and ammonia, I used the fact that oxygen is more electronegative than nitrogen and will be able to stabilize the charge better. So water will be more acidic than ammonia.Now how do I compare ammonia and ethyne?

• sodamide is used to deprotonate alkynes – Waylander Apr 12 at 6:57

Ethyne contains $$\mathrm{sp}$$-carbon and as a result the electronegativity of the carbon in ethyne is more than $$\mathrm{sp^3}$$ due to increased $$\mathrm{s}$$-character (50%) in the bonds between the carbon atoms.
The electronegativity of the carbon increases to a great extent when and turns out to be 3.2, which is greater than the electronegativity of nitrogen which is 3.04. Hence the hydrogen of ethyne is more acidic than that of $$\ce{NH3}.$$
• If it is ethene in place of ethane then $NH_3$ will be a better acid than ethene as in ethene the electronegativity of $sp^2$ carbon is 2.74 (33%s character)which is less than that of nitrogen – Harsh Wasnik Apr 12 at 16:04