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I’ve seen the video etc of sodium being put into freshwater and the reaction of flames/small explosion but I wonder if the same reaction would occur if conducted in salt water such as the ocean.

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Yes, sodium metal is also going to react exothermically with salt water or any other aqueous solution as long as it comes in contact with water:

$$\ce{Na (s) + H2O -> Na+ (aq) + OH- (aq) + 0.5 H2 (g)}$$

eventually leading to explosion of hydrogen-oxygen mix forming near the water surface. Presence of sodium chloride in salt water isn't going to influence the reaction as it neither capable of shifting equilibrium to the left (gas formation), nor passivate sodium metal surface as it would do, for instance, some viscous oil.

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    $\begingroup$ According to this post, this is an incomplete explanation of the reason for explosion. $\endgroup$
    – Ruslan
    Commented Jan 21, 2019 at 20:11
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    $\begingroup$ @Ruslan Of course it's incomplete because that's not what OP asked about. Thanks for providing the URL, now those who are also interested in how the detonation occurs, may quickly find the answer:) $\endgroup$
    – andselisk
    Commented Jan 21, 2019 at 20:16
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Sodium catches fire even in humid atmosphere. Salt water will make no difference. It will react with water in solution of salt in water, and the heat evolved will be very high and will vapourize sodium and it will fly away and may cause injuries. Do not do this at home.

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Yes it will, I tried it once, with 2 kgs straight into the Atlantic ocean. It'll sink, fizzle a little, pretending to be all over, and then roar up like a red hydra with molten sodium sputtering everywhere. It experiences as an explosion, though I am sure nitpickers will say it was only a very vigorous fire.

Rowing a boat that was on fire, with oars that were on fire, I claim the right of definition. It decidedly explodes.

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  • $\begingroup$ I upvoted because 1) you did (and survived) the bucket list experiment every chemist wants to do, whether or not they would admit to it, and 2) the boat and oars were on fire! Bravo! $\endgroup$
    – Ed V
    Commented Feb 7, 2022 at 17:01
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    $\begingroup$ Shot-putting sodium from a rowboat: a new olympic sport! $\endgroup$
    – Buck Thorn
    Commented Feb 7, 2022 at 20:05
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    $\begingroup$ @BuckThorn You have to have a NaK for it! ;-) $\endgroup$
    – Ed V
    Commented Feb 7, 2022 at 23:36
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    $\begingroup$ @EdV When the professor asks you to destroy what is surplus on the old chemicals storage in advance of the government inspection you do what you must ;). But I still defend my decision not to touch the 60 year old organic peroxides (they had crystals rimming the flask stoppers - a very gentle but firm message to not even consider touching the flasks. "Here be unknown and unstable depositions...") $\endgroup$
    – Stian
    Commented Feb 10, 2022 at 8:51
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    $\begingroup$ Well noted! When one of our professors retired due to Alzheimer illness, his lab had several pounds of NaK to be safely eliminated. Our campus Environmental Health and Safety folks treated it like a leftover WW II bomb and “neutralized” it in a parking lot well away from main campus, i.e., where new hires get their parking. ;-) I wouldn’t have gone near the peroxides either. Years ago, we had multi-pounds of old potassium that was removed because of the peroxide possibility. $\endgroup$
    – Ed V
    Commented Feb 10, 2022 at 12:45

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