Fundamentals F

[SamanthaTolentino 3D]

A student prepared a solution of sodium carbonate by adding 2.111 g of the solid to a 250.0-mL volumetric flask and adding water to the mark. Some of this solution was transferred to a buret. What volume of solution should the student transfer into a flask to obtain (a) 2.15 mmol Na1; (b) 4.98 mmol CO322; (c) 50.0 mg Na2CO3?

I calculated the molarity of Na2CO3 as .0796 M Na2CO3 but I don't know where to go from there. I looked at the solution but I don't understand why they set it up they way they did. Thank you!

[Olivia Yang 3J]

It looks like this question is actually in fundamental G (G.5) so I included a pic of how I solved the problem! When you get the molarity you should multiply by two for the 2 Na in Na2CO3. Then convert the 2.15 mm to moles and divide the moles by the Na molarity (0.159M)

[Leyla Anwar 3B]

For this problem why would the Na be multiplied by 2. Also, do the charges of the elements affect how this problem is solved?