Question

If 100 cm³ of 1.00 mol/dm³ HCl is added to 1.9 dm³ of water, what is the molarity of the new solution?

a) 0.05 mol/dm³
b) 0.10 mol/dm³
c) 0.15 mol/dm³
d) 0.20 mol/dm³

Answer 1

After diluting 100 cm³ of 1.00 mol/dm³ HCl in 1.9 dm³ of water, the molarity of the resulting solution is 0.050 mol/dm³, corresponding to option a) 0.05 mol/dm³.

Step-by-step explanation:

To determine the molarity of the new solution when 100 cm³ of 1.00 mol/dm³ HCl is added to 1.9 dm³ of water, we can use the concept of molarity and dilution. First, convert the volume of HCl from cm³ to dm³, which gives 0.100 dm³.

Then, calculate the number of moles of HCl in the initial 100 cm³ solution by multiplying the volume by the molarity (0.100 dm³ × 1.00 mol/dm³ = 0.100 mol). After adding this to the water, the total volume of the solution becomes 2.0 dm³ (1.9 dm³ + 0.100 dm³). Finally, to find the new molarity:

Molarity (M) = total moles of solute ÷ total volume of solution

0.100 mol HCl ÷ 2.0 dm³ = 0.050 mol/dm³

Therefore, the molarity of the new solution is 0.050 mol/dm³, which corresponds to option a) 0.05 mol/dm³.