[2E] Destroy Water on Acid

[JadedDM]

We're playing some Dragonlance, and we're fighting a lot of Kapak Draconians. For those who don't know, upon death they turn into puddles of acid.

The party cleric asked me whether a Destroy Water (the reverse of a Create Water) spell could dispel the acid.

Honestly, I'm not sure. What are some other opinions on this. Could Destroy Water dispel acid?

[CarpeGuitarrem]

Chemically, there's a lot of different compounds that could be acid, but none of them are fluids that consist of water + something. They are totally distinct from water.

Essentially, they'd have more grounds for draining an enemy of blood (plasma is mostly water) with this spell than destroying the acid. It's the same question as "can you use Destroy Water to get rid of oil?"

[hamlet]

Destroy water would, in my view as a DM, dry up the acid, but would do nothing about the actual acidity. The compound that is, itself, caustic would not be eliminated by the spell, but perhaps made slightly less dangerous. As undangerous as a highly caustic powder, for example, could be.

[Geostationary]

Basically what Hamlet said. If you assume that the acid is dissolved in water, than you're going to end up with concentrated acid crystals, which while less fluid are still pretty dangerous. It just makes it easier to handle in some ways, so long as they don't 1)step/fall in it or 2) allow it to vaporize or something. I've lost hairs just from standing near a jar of concentrated HCl. It's not fun stuff.

[The Random NPC]

Chemically, there's a lot of different compounds that could be acid, but none of them are fluids that consist of water + something. They are totally distinct from water.

Essentially, they'd have more grounds for draining an enemy of blood (plasma is mostly water) with this spell than destroying the acid. It's the same question as "can you use Destroy Water to get rid of oil?"

What a coincidence, I have a poem that describes this.

[Siosilvar]

Chemically, there's a lot of different compounds that could be acid, but none of them are fluids that consist of water + something. They are totally distinct from water.

Uh, what? Last time I took Chem, acids were things that shed protons when dissolved in water. All of them are fluids that consist of water + something.

D&D tends to use common terms, though, which would mean that an "acid" is pretty much any corrosive or caustic substance, only some of which are strictly acids. The ones that aren't wouldn't be affected.

I'd say it's a clever idea, so let them get away with it, drying it up the way hamlet and Geostationary described.

[Geostationary]

Uh, what? Last time I took Chem, acids were things that shed protons when dissolved in water. All of them are fluids that consist of water + something.

D&D tends to use common terms, though, which would mean that an "acid" is pretty much any corrosive or caustic substance, only some of which are strictly acids. The ones that aren't wouldn't be affected.

I'd say it's a clever idea, so let them get away with it, drying it up the way hamlet and Geostationary described.

For a given definition of acid, yes, but broader definitions only require that the molecules in question be an electron acceptor and an electron donor (Lewis acids), making the proton unnecessary. Bronsted-Lowry acids only require that the relevant reaction transfer a proton, which is what you appear to be referring to, but it doesn't necessarily involve water. The water's important most of the time, as it provides 1)a proton donor and 2)an aqueous solution, but is not in all cases necessary, but this is generally not terribly important to the conversation at hand. I would agree with your assertion that "acids" covers most corrosive/caustic chemicals in D&D, and the players should probably get away with it though.

[CET]

Short answer:
Hamlet's answer is probably about as good as you're going to get without getting into more chemistry than most folks are probably comfortable with. Since pretty much any 'acid' in the D&D sense could be a solution of the acid in water, saying that 'Destroy Water' leaves you with a small pool (or chalky residue, or gas) of concentrated acid is reasonable.

Long answer:
It depends. I think it's safe to assume that 'acids' in a D&D game are Bronsted-Lowry acids like Hydrochloric Acid, Nitric Acid, or Sulfuric Acid. I can't even get most of my first-year organic students to develop a working understanding of Lewis Acidity, so I'm inclined not to introduce it to a D&D game. Though I have had NPC alchemists use PCl3 as a chemical weapon . . . :)

Of the likely acids for a D&D setting:

Hydrochloric acid is actually a solution of Hydrogen Chloride Gas dissolved in water, so 'Destroy Water' would liberate HCl gas, but would get rid of the puddle.

Sulfuric Acid and Nitric Acid are both liquids in their pure form, so 'Destroy Water' won't disperse them, but if they were dissolved in water it would remove the water and leave you with a smaller amount of pure acid.

There are other strong Bronsted Acids (p-Toluenesulfonic acid, etc) that are solids in their pure form, and would leave crusty residue after a 'Destroy Water.' But these are mostly recent inventions (last 200 years or so) and not something you would expect to encounter in a D&D game.

[LibraryOgre]

In D&D, generally, "acid" is distinct from "water". "Destroy water" would not, IMO, get rid of acid; you'd be better off casting "Create Water" to heavily dilute it (a time-honored method of dealing with acid in D&D)

[JadedDM]

Interestingly enough, another one of my PCs brought up the idea of using Create Water to dilute the acid. That only raises the question, though, how much would it dilute it?

[hamlet]

Interestingly enough, another one of my PCs brought up the idea of using Create Water to dilute the acid. That only raises the question, though, how much would it dilute it?

That would get to a level of chemistry that's, for the most part, beyond the point of practicality within the game, which is why I liked the shorter version of "destroy water" actually destroying the acid, or dramatically reducing it, instead. It seems, in my head, a little easier to handle at table.

In terms of dilution? I . . . dunno. Depends on the type of acid (i.e., how much damage it does) and how much water in proportion to acid we're talking. If somebody was able to create an equal amount, in volume, of water as there is acid, then I'd say you've just reduced the damage by 50%. However, you've increased the area by 100%, so roll some saving throws those who were standing too close.

But it's been explained to me that I'm evil, so take that with a grain of salt.

[LibraryOgre]

Truthfully, I'd have the water reduce the effective duration... something like every level of the caster reducing the duration of the acid by 1 round (so a 6th level caster... impressive in DL standards... always negates a kapak).

It's not perfect, but it's easy to calculate.

[Autolykos]

What Hamlet said. The only interesting question would be whether the spell leaves you with the concentrated acid or the anhydride. In most cases, the concentrated acid is slightly less dangerous than the diluted version, but with others (like hydroflouric acid), it might backfire.
You should also keep water away from it at all costs (unless you like hot acid splashing everywhere). And remember that you're mostly water.

[erikun]

Destroy water would, in my view as a DM, dry up the acid, but would do nothing about the actual acidity. The compound that is, itself, caustic would not be eliminated by the spell, but perhaps made slightly less dangerous. As undangerous as a highly caustic powder, for example, could be.
I agree with this, except for the bolded part. You'll now have a substance that not only retains its acidity, but is also now highly hydrophilic. (It aggressively combines with watch to form the acid again.) It might make an interesting attempt to collect the acid, but won't likely make the area any less dangerous to pass through.

There is also the problem that acid won't necessarily turn into a solid upon removal of water. Hydrogen Chloride, for example, is a gas.

Geostationary is correct that there are acids which do not need to be dissolved in water. (There are also acids strong enough that they basically consume the water they are dissolved in.) I'm not sure how frequent or rare such a substance would be when talking about a D&D "acid". Most people probably think Hydrochloric or Sulfiric acid when the term is used, no doubt. [Edit] Please note that both of these produce a toxic gas if water were forcefully removed, making that a dangerous tactic.

[Winter_Wolf]

Professor CET, wouldn't turning HCl into a gas make it more dangerous to the people involved?

I am someday totally going to try and find a use for turning liquid acid into acid vapor and burning the lungs out of PCs. Because I'm not the "no" DM, I'm the "let's see what happens" DM (retired). **evil chuckle**