How can I solve this set of equations using the Symbolic Toolbox?

Hi guys,

I am trying to solve a set of equations for a chemical equilibrium for the concentration of H2S using the symbolics toolbox and the solve function. I have the following code. In this system, the concentrations HS, H2S and S are unknown. The equilibrium constants K1 and K2 and the concentrations H2O, H and Stot are known as well.

syms HS H2S H K1 K2 Stot S H2O;
eqns=[K1==(HS*H)/(H2O*H2S),K2==(S*H)/(H2O*HS),Stot==S+HS+H2S];
solve(eqns,H2S);

To me, this is a system that contains three unknowns and three equations. However, when running this code, it fails to find a solution for H2S. What do I need to change to make this work?

Thanks in advance for any and all help!

Answer 1

[Walter Roberson]

You need to solve for the same number of variables as you have equations.

[Joris Bergman]

Thanks Walter!

I did not know this before, as I am new to the symbolic toolbox.

You saved me a lot of headache today :)