The concentration of the diluted salt solution decreased
When a solution is diluted the concentration of then solution decreases and the volume of the solvent increases.
In this case;
The initial concentration is 0.50 M
The initial volume is 10.0 mL
The volume after dilution is 100 mL
We are required to determine the change in the final concentration;
According to the dilution equation;
M1V1 = M2V2
M2 = M1V1 ÷ V2
Therefore;
M2 = (0.5 M × 10.0 mL) ÷ 100mL
   = 0.05 M
Therefore, the concentration of the solution decreased after dilution.
