Question

You need to prepare 2.00 L of 0.100 M Na2CO3 solution. The best procedure is to weigh out: ___________

A. 21.2 g Na2CO3 and add 2.00 L of water to it.
B. 10.6 g Na2CO3 and add 2.00 L of water to it.
C. 21.2 g Na2CO3 and add water until the final solution has a volume of 2.00 L.
D. 10.6 g Na2CO3 and add water until the final solution has a volume of 2.00 L.

Answer 1

Answer:

The answer to your question is letter C

Explanation:

Data

Volume = 2 L

Molarity = 0.100 M

Molecular weight Na₂CO₃ = (2 x 23) + (1 x 12) + (3 x 16)

                                           = 46 + 12 + 48

                                           = 106 g

Process

1.- Calculate the grams of Na₂CO₃ needed

                         106 g ----------------  1 mol

                           x      ----------------  0.1 moles

                           x = (0.1 x 106) / 1

                           x = 10.6 g

2.- Calculate the grams of Na₂CO₃ needed for 2 liters of solution

                           10.6 g -------------- 1 liter

                            x        --------------  2 liters

                           x = (10.6 x 2) / 1

                           x = 21.2 grams of Na₂CO₃