All of the reagent solutions have a concentration of 0.2 M. This means that there is 0.2 mole of dissolved substance per liter of solution. What will be the concentration after mixing, assuming you use equal volumes of each solution?
Depends how many solutions you have. Concentrations or molarities can only be expressed with respect to each dissolved species....
The concentrations will therefore reduce in proportion to the mix ratio. If we had two solutions and mixed equal volumes the concentration of each species would reduce by a factor of 1:2. If we had 4 solutions each of 0.2M and mixed together equal volumes of each, the concentrations of each would reduce by a factor of 1:4.
Here's an example. Lets assume we have 0.2M copper sulphate solution, and 0.2M sodium chloride solution.
Now lets mix together 500 ml of each solution.
In 500 ml of 0.2M copper sulphate solution we have 0.1 moles of copper sulphate. In 500 ml of 0.2M sodium chloride solution we have 0.1 moles of sodium chloride.
The mixture has a total volume of 1000 ml, so the concentration with respect to copper sulphate will be (0.1 / 1000) = 0.1 mol/litre or 0.1M. The concentration with respect to sodium chloride will also be (0.1 / 1000) = 0.1 mol/litre or 0.1M.