If 12 L of a 1.4 mol/L hydrochloric acid (HCl) solution is mixed with 7 L of a 0.75 mol/L HCl solution, How many moles of HCl are in the final mixture?

Question

The mole (mol) is a unit used to describe the amount of an element or compound. The concentration of a chemical solution is often described as the number of moles of compound per litre of total solution (mol/L). If 12 L of a 1.4 mol/L hydrochloric acid (HCl) solution is mixed with 7 L of a 0.75 mol/L HCl solution, How many moles of HCl are in the final mixture? Round to 2 significant digits.

Final amount of HCl =

 _____mol

Answer 1

1.) Multiply the volume by the concentration to cancel out the units and obtain the moles. This is a common used in chemistry.

2.) Add the moles from each mixture to obtain the final moles in the mixture.

12 L x 1.4 mol/ 1 L = 16.8 mol HCl

7 L x 0.75 mol/ 1 L = 5,25 mol HCl

Total = 16.8 mol HCl + 5,25 mol HCl = 22.05 mol

Rounded to 2 significant figures, the answer is 22 moles.