The melting point of salt
- Thread starter jason2459
- Start date
- Tagged users None
Randy Holmes-Farley
Reef Chemist
Staff member
Super Moderator
Excellence Award
Expert Contributor
Article Contributor
R2R Research
My Tank Thread
wow!
fab
Active Member
What caused the explosion?
Did melting the salt somehow free up some elemental sodium which then reacted violently with oxygen in the water?
Was this a tank of saltwater or freshwater? Would it have mattered which it was?
Did melting the salt somehow free up some elemental sodium which then reacted violently with oxygen in the water?
Was this a tank of saltwater or freshwater? Would it have mattered which it was?
OP
OP
jason2459
Not a paid scientist
- Joined
- Jul 28, 2015
- Messages
- 4,668
- Reaction score
- 3,197
I don't have Facebook (and don't want one) otherwise I would message them and ask on their page if it was fresh or salt water in the tank. I doubt it matters.
https://m.facebook.com/RocketsAreCool/?refid=52&__tn__=C
KingBlingTX
Active Member
It's not a chemical reaction. The steam just forms so fast that the rapid expansion causes an explosion.
Randy Holmes-Farley
Reef Chemist
Staff member
Super Moderator
Excellence Award
Expert Contributor
Article Contributor
R2R Research
My Tank Thread
I was surprised at first at the intensity of the reaction, but I suspect it was just the rate at which the steam was made that cause a shock wave that burst the tank.
Let's calculate!
Say 2 cups (~510 grams) of molten sodium chloride. About 8.7 moles.
melting point = 1474 deg C according to the video. Let's assume it is just at its melting point and not above.
Heat of fusion of sodium chloride= 27.95 kJ/mol
So we get 8.7 moles x 28 kJ/mol = 244 kJ of energy released as it solidifies.
Now look to the energy as it cools from 1474 to 100 deg C. That is 1374 degrees and 8.7 moles.
The heat capacity of solid NaCl is 50 J/(mol K) so the heat of cooling is about 50 x 8.7 x 1373 = ~600 kJ
So the molten salt could deliver about 600 kJ to the water.
Now look at the water
The heat of vaporization of water is about 40.7 kJ/mole
The heat capacity is about 75 J/(mol K)
So to raise 1 mole of water at 25 C to steam at 10o deg C takes about 40.7 kJ + 75 J/(mol K) x 75 (deg C) = 46 kJ
OK, so now we see that we could possibly vaporize about 600/46 = 13 moles of water, assuming we only heated that water and no other water.
13 moles (234 g) of vapor water will take up about 364 liters at 100 deg C.
So even if we only vaporize 1/10th of the theoretical amount (26 L), if that happens fast enough it would certainly explain what we saw.
And, I hope I did these quick calculations correctly.
Let's calculate!
Say 2 cups (~510 grams) of molten sodium chloride. About 8.7 moles.
melting point = 1474 deg C according to the video. Let's assume it is just at its melting point and not above.
Heat of fusion of sodium chloride= 27.95 kJ/mol
So we get 8.7 moles x 28 kJ/mol = 244 kJ of energy released as it solidifies.
Now look to the energy as it cools from 1474 to 100 deg C. That is 1374 degrees and 8.7 moles.
The heat capacity of solid NaCl is 50 J/(mol K) so the heat of cooling is about 50 x 8.7 x 1373 = ~600 kJ
So the molten salt could deliver about 600 kJ to the water.
Now look at the water
The heat of vaporization of water is about 40.7 kJ/mole
The heat capacity is about 75 J/(mol K)
So to raise 1 mole of water at 25 C to steam at 10o deg C takes about 40.7 kJ + 75 J/(mol K) x 75 (deg C) = 46 kJ
OK, so now we see that we could possibly vaporize about 600/46 = 13 moles of water, assuming we only heated that water and no other water.
13 moles (234 g) of vapor water will take up about 364 liters at 100 deg C.
So even if we only vaporize 1/10th of the theoretical amount (26 L), if that happens fast enough it would certainly explain what we saw.
And, I hope I did these quick calculations correctly.
120reefkeeper
Reef keeping with Military Precision!
- Joined
- Jan 5, 2016
- Messages
- 3,956
- Reaction score
- 7,801
- Location
- Las Marias, Puerto Rico
- What state or country do you live in
- Other International
You know I'm not a super scientific guy but I think that adding that salt to the water breaks the hydrogen molecules loose. I've seen this type of reaction in my industry before. I work in a steel mill and when on a rare occasion liquid steel"2800 degrees" meets water and Boom! We call it a break out and it is devastating. Basically a hydrogen bomb! It's very important for us that water is used to cool the steel, not the other way around.
Randy Holmes-Farley
Reef Chemist
Staff member
Super Moderator
Excellence Award
Expert Contributor
Article Contributor
R2R Research
My Tank Thread
I'm not sure what you mean, but I do not believe that mixing hot sodium chloride and water will make H2.
Steel is different, since it has metals like iron in the zero oxidation state. Iron can react with H+ or just water (in the absence of sufficient O2) to form H2:
Fe(s) + 2H+(aq) → Fe2+(aq) + H2(g)
120reefkeeper
Reef keeping with Military Precision!
- Joined
- Jan 5, 2016
- Messages
- 3,956
- Reaction score
- 7,801
- Location
- Las Marias, Puerto Rico
- What state or country do you live in
- Other International
I'm not sure what you mean, but I do not believe that mixing hot sodium chloride and water will make H2.
Steel is different, since it has metals like iron in the zero oxidation state. Iron can react with H+ or just water (in the absence of sufficient O2) to form H2:
Fe(s) + 2H+(aq) → Fe2+(aq) + H2(g)
Wouldn't the thermal expansion of the water molecules cause the H2O to break the H2O bond?? Thus separating the Hydrogen from the oxygen??
Or all we are seeing in the video is thermal expansion? Aka shockwave??
Makes me wonder if there isn't more going on here than we can see.
120reefkeeper
Reef keeping with Military Precision!
- Joined
- Jan 5, 2016
- Messages
- 3,956
- Reaction score
- 7,801
- Location
- Las Marias, Puerto Rico
- What state or country do you live in
- Other International
I also noticed the color of the liquid salt was odd?? Possible reaction to the atmosphere or the vessel that it was heated in?? The salt could have picked up some other elements from that vessel it was melted in.
Randy Holmes-Farley
Reef Chemist
Staff member
Super Moderator
Excellence Award
Expert Contributor
Article Contributor
R2R Research
My Tank Thread
According to wikipedia, water begins to decompose at temps over 2200 deg C
https://en.wikipedia.org/wiki/Water_splitting
"At elevated temperatures water molecules split into their atomic components hydrogen and oxygen. For example, at 2200 °C about three percent of all H2O molecules are dissociated into various combinations of hydrogen and oxygen atoms, mostly H, H2, O, O2, and OH. "
But that is an endothermic process (takes up heat energy) and if it "burned" back to water, the net round trip is an energy neutral and volume neutral process.
So I do not think this explains what happened in the video.
Randy Holmes-Farley
Reef Chemist
Staff member
Super Moderator
Excellence Award
Expert Contributor
Article Contributor
R2R Research
My Tank Thread
I'm not sure what they started with or what color to expect, but I would guess that part of the reddish color may have been black body radiation as opposed to reflected/absorbed light.
At 1450 deg C (1700 K), one expects some reddening:
https://en.wikipedia.org/wiki/Color_temperature
