Max Emp Acid Arrow shoots 1 arrow that does 8+1d4 when it hits, and 8+1d4 for the next 4 rounds at level 13.
2 such spells would do 80+10d4 total. He probably thinks it did 120x3 because hes maximizing the empowered damage, which isn't how those metamagics work when used together, and mixing up 2 level 2 blasting spells.
Er, no.
An empowered magic missile deals x1.5 times its normal damage (roll 1d4+1 and multiply the result by 1 1/2 for each missile).
You calculate the damage, THEN you multiply. As for how maximize and empower interact, that is a specific exception that was established in the PHB. You calculate max damage, then you multiply by 1.5. By the wording of the feats, that shouldn't happen. It's either empower OR maximize. They have specific rules that basically state, "In this situation, it works like this."
Your player probably got scorching ray and acid arrow confused as well, scorching ray gives 3 shots per spell, acid arrow only gives 1. The 2 mistakes together would give 360 damage per spell, about 3.6x what he should have gotten. Only you can decide if it was an honest mistake.
As good an explination as any.
I don't know where Captnq learned chemistry, but neither water nor dirt neutralizes acid. And that's even assuming that real-world physics applies in this case; which we really have no reason to believe. It is quite likely that they gave us an option (neutralize the acid), but didn't give us any means to actually do that.
Are there any rules anywhere for acid-base interaction in d&d?
I learned it from having acid thrown on me. I ran to the eye wash station where the acid was washed away by water being jetted out. Ever inhale acid that's gone air born? Your lungs stop working. You reflexively force all the air out and your lungs REFUSE to take in any air. It's sort of weird, standing there, in control of the rest of your body, but unable to get your diaphragm to relax, trying desperately to get air to go back into your lungs.
So let me assure you, massive amounts of water diluted the acid. When you add water you make the over all acidity go down because acidity is a matter of concentration. If you are reducing acidity, that's called, neutralizing.
You can also add salt. Salt, which I might add, is a common factor in rock. By the way, I'm not talking about table salt, but Ionic Salts that form from an acid and a base. Ionic salts of any form introduced to Acid or Base materials in a solution tend to screw up the reaction and weaken the over all exchange of Hydrogen ions and Hydroxide ions. Most of your antacids that people take for heartburn are a variation on this. You don't swallow Base materials to neutralize the acid, that would cause damage to your throat as you swallow. You swallow instead Ionic Salts.
Most people don't know that the acid itself isn't dangerious. It's the interaction with water that allows the build up of excessive Hydrogen ions. Sodium is actually harmless, until it comes in contact with water... like water vapor. Then it bursts into flames as it causes the H2O to break down into NaOH and H+ that evaporates into the air. The resulting exothermic reaction produces enough heat to cause the hydrogen to burst into flames.
IMPORTANT SAFETY TIP: If you ever find yourself cleaning out Your highschool's old chemical locker and you are told to throw out everything and find a bottle of brownish fluid and a block of sodium that weighs 5 pounds. Do not go to your local open sewer, put it on a raft, push in into the open water, then throw rocks at it.
EXPLOSIONS ARE BAD!
MAKING WATER BURN IS BAD!
SETTING A SEWER ON FIRE IS BAD!
Although watching blue-white flames shooting everywhere
is kinda cool.
IN SHORT:
1. Dilute the acid with water (Best Choice)
2. Mix ionic salts in with the acid.
3. Take fluid absorbing material (dust, dirt, and/or chalk) and rub it over the acid, thus giving the acid something else to interact with besides your skin, and hopefully making it easier to scrape the acidic substance off.
Of the above choices, 2 gallons of water going SPLOOSH from a create water cantrip cast by a 1st level cleric seems the most effective choice.