Question

While cleaning a toilet, 150 mL of disinfectant solution is poured into a toilet containing 750 mL of water. If the initial concentration of the disinfectant was 3.40 mol/L, determine the new concentration of the solution.

Answer 1

How any mols disinfect did you have ?

(3.40 mol / 1000 mL) (150 mL) = 0.51 mols used
total volume = 150 + 750 = 900 mL = 0.9 L
so
0.51 mols / 0.9 L = 0.567 mols / liter