Chemistry problem

Question

A student has 5.70 g5.70 g of zinc powder, 1.05 L1.05 L of a 3.10 M3.10 M calcium nitrate solution, and 1.60 L1.60 L of a 2.10 M2.10 M lead(II) nitrate solution.

Write the chemical reaction that occurs between the two reacting species. Include physical states.

molecular equation:

What volume of the solution is needed to completely react all 5.70 g5.70 g of zinc powder?

volume: L

Calculate the molarity of the Zn2+Zn2+ ions in the solution after the reaction.

concentration: M

Answer 1

If you look at the activity series for metals, you will find that Zn is more reactive than Pb, and so will replace it. However, Zn is LESS reactive than Ca, and so it will not replace it. So, the two reacting species will be

Zn and Pb(NO₃)₂

Molecular equation:

Zn(s) + Pb(NO3)(aq) ==> Zn(NO3)2(aq) + Pb(s)

5.70 g Zn(s) x 1 mol Zn(s) / 65.4 g = 0.0872 moles Zn(s)

0.0872 mols Zn x 1 mol Pb(NO₃)₂ / 1 mol Zn = 0.0872 mols Pb(NO₃)₂ needed

0.0872 mols Pb(NO₃)₂ x 1 L / 2.10 mols Pb(NO₃)₂ = 0.0415 L Pb(NO₃)₂ needed

Molarity of Zn²⁺ after reaction:

0.0872 mols Zn(NO₃)₂ = 0.0872 mols Zn²⁺

Total volume = 0.0415 L

[Zn²⁺] = 0.0872 mols / 0.0415 L = 2.10 M