Reef Chemistry Question of the Day #197 Boiling Point of Seawater

[Randy Holmes-Farley]

Reef Chemistry Question of the Day # 197

Under conditions where the boiling point of pure fresh water is 100°C, what is the boiling point of 35 ppt seawater?

Just pick the one that seems most right to you. The data on the internet is variable and often wrong.

A. 97 °C
B. 100°C
C. 100.5 °C
D. 105 °C
E. 130 °C

Good luck!

































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[Rybren]

I would think that the boiling point of SW would be higher than FW, but I have no idea how much higher.

I'll take a WAG and say D. 105 degrees.

 

[Zero Nitrates]

A.
You add salt to water on the stove so it boils faster.

 

[iheartsps]

A

 

[Myka]

A

Both the boiling point and the freezing point of saltwater is lower than freshwater. Altitude also affects these points.

 

[JimWelsh]

The way I read Raoult's Law, the non-volatile solutes in seawater will lower the vapor pressure of the solution, which will depress the freezing point, but raise the boiling point. DeltaT = Kbp * bSW = about 0.5, so I'm going with C. Yes, I cheated, but I learned something, too. My WAG was going to be D.

 

[_Conway]

C
Boiling point increase slightly.
time to boil decreases

 

[Myka]

A

Both the boiling point and the freezing point of saltwater is lower than freshwater. Altitude also affects these points.

I realize I messed up. I didn't cheat like Jim yet though.

The boiling point is higher in saltwater than freshwater, the amount of energy used to boil the water is less, so given all else is equal it takes less time (say adding salt to water you're going to boil on the stove).

So instead of "knowing" the answer, my WAG is D.

I still stand by the altitude comment though, haha!

 

[SROPE]

A . For me.

 

[Lynn52]

C

 

[DamianOZ]

D

 

[jason2459]

C. 100.5 °C

water boiling point = 100 °C
+0.514°C/molal unit for boiling
-1.855°C/molal unit for freezing

If S = 35PSU

Then seawater = 1.12 mol

Boiling point = 100.57568°C

Water is some awesome stuff. Especially saltwater.

 

[jason2459]

I realize I messed up. I didn't cheat like Jim yet though.

The boiling point is higher in saltwater than freshwater, the amount of energy used to boil the water is less, so given all else is equal it takes less time (say adding salt to water you're going to boil on the stove).

So instead of "knowing" the answer, my WAG is D.

I still stand by the altitude comment though, haha!

Pressure will impact it's ability to vaporize. Enough pressure and temp and you can have the liquid and vapor at the same density. Go beyond that temp and just vapor.

 

[GMay]

C or D. The addition of a solute will lead to a freezing poor depression and a boiling point at STP.

 

[amppdx]

Answer is A. Adding dissolved ions disrupts the bonds between the water molecules and allows them to phase transition to gas at a lower temp.

 

[jason2459]

...
Water is some awesome stuff. Especially saltwater.

Don't want to derail this QOD thread to much so created this thread here :

http://reef2reef.com/threads/water-the-uncommon-common-molecule.246094/

I love studies on water. It's properties are so very unique.

 

[todda5914]

B. I don't think anything in saltwater would lower or raise the boiling point.

 

[Philip Chin]

b

 

[reynaldoramon]

Do we get the correct answer from professor Holmes-Farley.

 

[HOOPDEEZ]

Reef Chemistry Question of the Day # 197

Under conditions where the boiling point of pure fresh water is 100°C, what is the boiling point of 35 ppt seawater?

Just pick the one that seems most right to you. The data on the internet is variable and often wrong.

A. 97 °C
B. 100°C
C. 100.5 °C
D. 105 °C
E. 130 °C

Good luck!








A!
























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