Question

 

1.Make a table in your notebook with the anions on one axis and the cations on the other axis. Make the boxes in the table large enough that you can write down values as well as observations.

Anions: NO₃^-, CO₃^2-, SO₄^2-

Cations: K⁺, Sr²⁺, Ag⁺

2.Look up and write down the value for solubility at 20 °C of each of each of the 9 resulting salts in the table (a value, not soluble/insoluble). It may help to use the “find” function in your web browser in the Wikipedia solubility table. Make sure you write down the units of the solubility.

3.Clean nine small test tubes with soap and water, rinse them with deionized water, shake the water out of them, and place them in a test tube rack. Add a few drops of the 0.10 M solutions that contain the ions on the table to the test tubes (pay attention to the concentrations on the bottles). Be sure to replace the droppers in their correct bottles. Mix the contents of the tube thoroughly by holding the top of the tube and snapping the bottom of the tube with your finger. Observe each tube for a precipitate. Record your observations in your table. Be sure to record the concentrations of solutions from the bottles.

4.Try mixing Ag⁺ and SO₄^2- again, but this time try using the 1.0 M Ag⁺ with 1.0 M SO₄^2-.

QUESTIONS

1. Look at the solubility guidelines below. Which of these are observable in your data?

2. When a precipitate forms, do any of the ions involved in the precipitate stay in solution?

3. Are there more strontium ions in solution in the presence of equal concentrations of carbonate or sulfate (use the solubility values you looked up to help)?

Solubility Guidelines

Soluble Ionic Compounds	Insoluble Ionic Compounds
1. Group 1A(1) ions (Li+, Na+, K+, etc.) and ammonium (NH4+)	1. OH–except with Group 1A(1), NH4+, and larger Group 2A(2)(beginning with Ca2+)
2. NO3–,CH3CO2–, and ClO4–	2. CO32–except with Group 1A(1) and NH4+
3. Cl–, Br–, I–except with Ag+, Pb2+, Cu+, and Hg22+	3. S2–except with Group 1A(1) and NH4+
4. SO42–except with Ca2+, Sr2+, Ag+, and Pb2+.	4. C2O4–2except with Group 1A(1), and NH4+.
	5. PO43–except with Group 1A(1) beginning with Na+, and NH4+.

Answer 1

QUESTIONS

1. Look at the solubility guidelines below. Which of these are observable in your data?

observable data is only --> production of a precipitate; formation of gas ( bubbles ) and dissolution (solid dilutes)

2. When a precipitate forms, do any of the ions involved in the precipitate stay in solution?

True, due to 2 reasons:

- Equilibrium will always have certain amount of SOLID and Aqueous solution ions... therefore, ions will be present,

- By stoichiometry, if there is excess of an ion, then this will not be precipitated, and it remains in solution

3. Are there more strontium ions in solution in the presence of equal concentrations of carbonate or sulfate (use the solubility values you looked up to help)?

Strontium Sr2+, will form precipitate with sulfate ions, SO4-2

Sr+2 + CO3-2 = SrCO3

Compare Ksp value, low amount of Ksp will favour solid formation

SrSO4 3.44×10–7

SrCO3 5.60×10–10

clearly, SrCO3 is Less than SrSO4, so expect MORE Sr2+ ions in SO4-2 solution than CO3-2 solution