Practice Problem 12.105 Part A You have 2500.0 mL of a 0.250 M solution of NaCl

Question

Practice Problem 12.105 Part A You have 2500.0 mL of a 0.250 M solution of NaCl How many moles of NaCl are present in this solution? Express your answer with the appropriate units. 0.625 mol Submit My Answers Give Up Correct Part B How many moles of ions are present in this solution? Express your answer with the appropriate units. mol Submit My Answers Give Up Incorrect: Try Again Part C How many grams of NaCl would you recover if you evaporated all of the water Express your answer with the appropriate units. 36.5 g Submit My Answers Give Up Correet Provi

Explanation / Answer

Ans. #1. Moles of NaCl = Molarity x Volume of solution in liters

                                    = 0.250 M x 2.50 L

                                    = 0.625 mol

#2. Dissociation of NaCl:     NaCl ----------> Na+ + Cl-

In water, each molecule of NaCl dissociates into two ions – Na+ and Cl-.

Therefore, 1 mol NaCl is equivalent to 2 mol ions.

So,

            Moles of ions = 2 x moles of NaCl

                                    = 2 x 0.625 mol

                                    = 1.25 mol

#3. After evaporation, all the water is lost leaving behind solid NaCl.

Mass of NaCl recovered = Moles of NaCl x Molar mass

                                    = 0.625 mol x (58.442468 g/mol)

                                    = 36.53 g

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