When 70.0 milliliters of 3.0-molar Na2CO3 is added to 30.0 milliliter of 1.0-molar NaHCO3, the Resulting concentration of Na 1 ions is (a) 2.0 M (b) 2.4 M (c) 4.0 M (d) 4.5 M (e) 7.0 M.

(d) 4.5 M

Explanation:

We have 70.0 mL of 3.0-molar Na₂CO₃. The moles of Na₂CO₃ are:

70.0 * 10⁻³ L * 3.0 mol/L = 0.21 mol

There are 2 moles of Na⁺ in 1 mole of Na₂CO₃. The moles of Na⁺ in 0.21 moles of Na₂CO₃ are 2 * 0.21 mol = 0.42 mol

We have 30.0 mL of 1.0-molar NaHCO₃. The moles of NaHCO₃ are:

30.0 * 10⁻³ L * 1.0 mol/L = 0.030 mol

There is 1 mole of Na⁺ in 1 mole of NaHCO₃. The moes of Na⁺ in 0.030 moles of NaHCO₃ are 1 * 0.030 mol = 0.030 mol

The total number of moles of Na⁺ is 0.42 mol + 0.030 mol = 0.45 mol

The total volume is 70.0 mL + 30.0 mL = 100.0 mL

The concentration of Na⁺ is

0.45 mol / 0.1000 L = 4.5 M