Question

100 mL of a 1 M HCL and 100 mL of a 5M NaCl solution are mixed. What is the final molarity of the chloride ions?

A.) .5M
B.) 2M
C.) 3M
D.) 4M

Answer 1

3M

Step-by-step explanation:

Because HCl and NaCl do not react with each other, the final number of the Cl⁻ ions is equal to the sum of the ions of each starting reagent:

• HCl → H⁺ + Cl⁻

Cl⁻ moles from HCl ⇒0.100 L * 1 M = 0.1 moles Cl⁻

• NaCl → Na⁺ + Cl⁻

Cl⁻ moles from HCl ⇒0.100 L * 5 M = 0.5 moles Cl⁻

• Total Cl⁻ moles = 0.1 + 0.5 = 0.6 moles Cl⁻

We add up the volumes from each solution:

• Final volume = 0.1 L + 0.1 L = 0.2 L

And finally calculate the final molarity of Cl⁻ ions:

• Final molarity = 0.6 mol / 0.2 L = 3M