Question

Please someone help explain this to me. Why does salt water boil at a lower temperature than tap water?

Answer 1

Note : I am taking the salt as table salt ( \(NaCl\) ) , just for an example.

For making salt water, you have to first dissolve \(NaCl \) (Sodium Chloride or Salt) in water (\(H_2 O\) ) . The ions in sodium chloride (\(Na^{+} \) and \(Cl^{-} \) ) get dispersed in water. As hydrogen bonding is present in \(H_2 O\) or water and it is hard to turn water into gas as it is a polar molecule. The ions in water, disrupts the hydrogen bonding and hence, this makes water boil at low temperature ( salt water ) .

See, pure water has high boiling point than tap water and tap water has high boiling point than salt water. Do you know why?

The pure water has no impurity to disrupt its hydrogen bonding while tap water has little salts also . But, salt water has the ions Na+ and Cl - which disrupts the hydrogen bonding.

Hope you got it.

Answer 2

Thank you so much. Thank you thank you thank you!

Answer 3

Glad your doubt is solved and it was helpful for you. :) Best of Luck

Answer 4

Really, thank you. I'm taking Chem and I had to do a project but the previous class work didn't give an explanation so I didn't understand the project very well. You're really great. Thank you, again!

Answer 5

You're welcome again . And good luck for chemistry study.

Answer 6

Interesting article : http://www.swri.org/10light/water.htm

Answer 7

@mathslover shouldnt impurities elevate the boiling point?

Answer 8

Isn't that factually incorrect. Salt water boils at a higher temperature than tap water, right?

Answer 9

Yes, thinking the same... I just got stick to the questions' language.

Answer 10

@aditkarekatte well, it should if it doesnt!

Answer 11

@mathslover then how would u explain what @thisshouldfeellikefire asked?

Answer 12

That was pretty much the essence of my question. Is it not a wrong question?

Answer 13

It's a wrong question? I don't understand. I did the experiment and the salt water boiled at a lower temperature than the tap water did.

Answer 14

Did you use pure water to dissolve the salt?

Answer 15

Well if its tap water, that doesnt necessarily mean its pure! Depends on the hardness of the tap water! It might have dissolved salts too! Pure water as in distilled water would boil at a temperature lower than tap water!

Answer 16

@thisshouldfeellikefire

Answer 17

the wording of the question is incorrect. water with impurities will boil at a higher temp than pure (distilled) water because the added ions create additional IMFs that the solvent molecules must overcome in addition to the H-bonding IMFs that are normally present in water. If a sample of "salt water" was made with distilled water, and compared to a sample of tap water, if the tap water boils at a higher temp, then there must be more ions in the tap water than in the salt water.