Physics and Chemistry cannot be separated

At a laboratory, there are two solutions inside beakers: $200 \text{ cm}^{3}$ of an aqueous solution of sodium hydroxide $0.3$ mole/L and $200 \text{ cm}^{3}$ of an aqueous solution of hydrochloric acid $0.25$ mole/L. These two solutions are mixed inside another beaker and the resulting solution is heated to $400^\circ C$ . What is the approximate concentration, in moles/L, of sodium ions on this resulting solution after the heating?

Details and Assumptions:

• Use the initial values to calculate things related to spilled liquid (if there is), as concentrations and number of moles.
• The laboratory's room temperature is 25°C and the system was, initially , in complete thermal equilibrium.
• Do not consider any heat release due to breakage of chemical bonds.
• The beakers' volumetric thermal expansion coefficient is $5 \times 10^{-5} °C^{-1}$ and the resulting solution's volumetric thermal expansion coefficient is $5.43 \times 10^{-4} °C^{-1}$ .
• Do not consider the middle stages of the heating process. Use in your calculations the values related to the moment after the heating.
• The resulting solution is unsaturated and its solutes are distributed homogeneously in the beaker's space.
• Do not consider any water production due to any chemical reaction.
• The beaker that contains the resulting solution is, at the end of all processes, completely full.
• Do not consider any volume contraction due to hydrogen bonds that might be formed.