[Ter]

HI I'd like to clarify this!

In testing for the enthalpy change for the reaction of two aqueous solutions, so far I know you use the insulating vessel nethod ie. polyestene cup to minimize heat loss and then extrapolate the temperature time graph etc. So to get q which is the heat absorbed or evolved ( is it by the system )? you need values for mc and change in temperature.
My question is, for mass, which mass do you use?

I know that for aqueous solutions you use the mass of the solution, just let ml = g. But now with two solutions, which do you use? I think it's the limiting reagent's mass you should use but then isn't it that these two solutions are mixed in a reaction, so the mass should be the mass of the two solutions?

Please help me out I'm confused!!

Thank you!

[Borek]

Please elaborate by giving example of a problem you are referring to.

[Wald_ron]

From my understanding,
you've mixed two samples together and then observed a temperature change which you've subsequently related back to your q.

Mass in this case is a constant. q is the heat released by the system. It is therefore a population term and you should use the total volume to relate back to mass.