Chemical reaction that can produce lots of heat from 2-3 simple liquid ingredients?

Have an experiment I want to try out utilizing thermoelectric power and I want to generate the heat via a simple chemical reaction. Ideally I'd like to mix 2 liquids together (one being water or alcohol would be great) that can get to around boiling water temperature for a few minutes or longer. Byproducts need to be only other liquids that can be drained easily or gasses that aren't dangerous to humans. No solids wastes and non corrosive / carcinogen / caustic.


So far I've found one that's close to my needs but still produces a solid waste product and isn't particularly safe, which is Calcium Oxide + Water -> Calcium Hydroxide + Heat. This might work if there's another liquid I could add after the main reaction to turn the Calcium Hydroxide into a liquid for disposal.




The first thing that comes to mind, if you have access to a stock-room, is mixing two solutions: (1) NaOH; (2) HCl. This can release a lot of heat if your solutions are concentrated enough, and it forms salt-water if your NaOH and HCl are of the same molarity. 


Edit: I'm on my lunch break, so I did some of the math... 


The chemical reaction of interest in this case is:


$$\ce{OH- + H+ -> H2O}$$


The standard enthalpies of formation ($\Delta H\_\mathrm f^\circ$) of these species are: 


$$\begin{array}{lr}
\hline
\text{Species} & ΔH\_\mathrm f^\circ/\pu{kJ mol-1} \\
\hline
\ce{OH-} & -229.99 \\
\ce{H+} & 0.00 \\
\ce{H2O} & -288.83 \\
\hline
\end{array}$$


Thus, the change in enthalpy for the reaction is: 


$$\Delta H^\circ = -288.83\ \mathrm{kJ/mol} - (-229.99\ \mathrm{kJ/mol}+0\ \mathrm{kJ/mol}) = -58.84\ \mathrm{kJ/mol}$$


Therefore, for $1\ \mathrm{mol}$ of $\ce{NaOH}$ + $1\ \mathrm{mol}$ of $\ce{HCl}$, you get $58.84\ \mathrm{kJ}$ of heat. Say you want to release enough heat to get the net solution up to $100\ \mathrm{^\circ C}$. 


Water has a heat capacity of $4.18\ \mathrm{J/(g\ ^\circ C)}$. Say you have $1\ \mathrm L$ of $\ce{NaOH}$ + $1\ \mathrm L$ of $\ce{HCl}$, you'll need enough heat to raise the temperature of $2\ \mathrm L$ of water to $100\ \mathrm{^\circ C}$. I'll assume the water starts off at $25\ \mathrm{^\circ C}$, so you have $2\,000\ \mathrm g$ and $75\ \mathrm{^\circ C}$ to go. 


$$4.18\ \mathrm{J/(g\ ^\circ C)} \cdot 2\,000\ \mathrm g \cdot 75\ \mathrm{^\circ C} = 62\,700\ \mathrm J = 62.7\ \mathrm{kJ}$$


How many moles of $\ce{NaOH}$ + $\ce{HCl}$ do you need for that much heat? 


$$\frac{q}{\Delta H^\circ} = \frac{62.7\ \mathrm{kJ}}{58.84\ \mathrm{kJ/mol}} = 1.065\ \mathrm{mol}$$


That would mean that you can mix $1\ \mathrm L$ of $1.065\ \mathrm M$ $\ce{NaOH}$ + $1\ \mathrm L$ of $1.065\ \mathrm M$ of $\ce{HCl}$, and would theoretically expect to get a temperature close to $100\ \mathrm{^\circ C}$. 


This might be off a bit because I've made some assumptions:


1. $\Delta H^\circ$ is constant with respect to temperature from $25\ \mathrm{^\circ C}$ to $100\ \mathrm{^\circ C}$. This may not be true.
2. the dissolved salts in water dont significantly affect its heat capacity
3. You have $2\,000\ \mathrm g$ of water in $1.065\ \mathrm M$ $\ce{NaOH}$ + $1.065\ \mathrm M$ $\ce{HCl}$


I think this could get you close though? I'm a bit surprised that the molarities aren't higher... It's a starting point at least.


Disclaimer of course: be careful with the $\ce{NaOH}$ + $\ce{HCl}$ solutions, they can be dangerous. Use proper chemistry hygeine protocols. The mixture should be benign, but you should confirm this with pH paper. 


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As Zhe says, this isn't safe. Your question mentions "draining" chemicals as if it's OK to dump chemicals down the drain or out on the ground. It's not. What possible connection is there between an exothermic chemical reaction and an experiment in thermoelectrics, I can't imagine. Use a hot plate. Here's a hint: heating water to its boiling point requires a lot of energy (per gram). Another name for a chemical reaction that produces a lot of energy is "an explosion". I can't think of any which someone who thinks "if its liquid, I can just dump it down the drain" would be safe to implement.


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