1. (a) What is the Na⁺ concentration in each of thefollowing solutions:

2.85 M sodium sulfate:

2.18 M sodium carbonate:

0.985 M sodium bicarbonate:

(b) What is the concentration of a lithium carbonate solutionthat is 0.395 M in Li⁺? M

2. A sample of 0.7160 g of an unknown compound containing bariumions (Ba²⁺) is dissolved in water and treated with anexcess of Na₂SO₄. If the mass of theBaSO₄ precipitate formed is 0.6894 g, what is thepercent by mass of Ba in the original unknown compound?

3. A 0.9080 g sample of a mixture of NaCl and KCl is dissolvedin water, and the solution is then treated with an excess ofAgNO₃ to yield 1.953 g of AgCl. Calculate the percent bymass of each compound in the mixture.

% mass NaCl

% mass KCl

4. The concentration of lead ions (Pb²⁺) in a sampleof polluted water that also contains nitrate ions(NO₃^−) is determined by adding solid sodiumsulfate (Na₂SO₄) to exactly 500 mL of thewater. Calculate the molar concentration of Pb²⁺ if0.00260 g of Na₂SO₄ was needed for thecomplete precipitation of lead ions as PbSO₄.

5. Consider the reaction

H₂(g) + Cl₂(g) →2HCl(g) Δ H = −184.6 kJ/mol

If 5.0 moles of H₂ reacts with 5.0 moles ofCl₂ to form HCl at 1.0 atm, what is Δ U forthis reaction? Assume the reaction goes to completion and ΔV = 0 L.
(The conversion factor is 1 L atm = 101.3 J.)