Chemistry solubility help please

Question

what mass of solute is needed to prepare 140 mL of 0.560 M KCI?

20.0 mL of water is added to 30.0 mL of 0.0500 M sodium carbonate. What is the concentration of sodium ions in the diluted solution?

Answer 1

140mL = 0.140L

0.140L x 0.560 = 0.0784moles of KCl

0.0784 moles x 74.6 g/mole = 5.85g of KCl needed

0.030 L x 0.0500 M = 0.0015 moles of Na2CO3

0.0015moles / 0.050 L = 0.030M Na2CO3

Because there are 2 moles of Na+ per mole of Na2CO3, you have a final [Na+] of 0.060M