Question

Determine the moles of Cl- in the salt based on the following experimental data.

10.00 mL of 1.00 M HCl solution is added to 0.080 g of Mg metal. The reaction goes to completion and all of the Mg metal is gone. After placing the resulting solution on a hot plate and allowing all water and excess HCl to volatilize off, 0.271 grams of salt remains in the beaker.

Answer 1

Mg + 2 HCl ----------------------> MgCl2 + H2

salt mass = 0.271 g

salt MgCl2 molar mass = 95.2 g / mol

moles of salt = mass / molar mass

                    = 0.271 / 95.2

                   = 2.85 x 10^-3

moles of Cl- = 2 x 2.85 x 10^-3

                    = 5.69 x 10^-3

moles of Cl-   = 5.69 x 10^-3