1. Interaction of sodium with air and water

(WARNING: put on protective glasses!)

a) Take a piece of sodium from a vessel with oil (use pincers), put it on a filter paper and cut it with a knife. What happens to the shining surface of sodium after some time?

b) Put a small piece of sodium into a porcelain dish filled with water. Add 1-2 drops of phenolphtalein as indicator.

2. Hydrolysis of salts of alkaline metals

Take some crystals of sodium acetate into a test tube and add distilled water until the salt dissolves. Measure pH of the solution with the help of the universal indicator. Repeat the experiment with sodium and potassium carbonates.

3. Decomposition of nitrates of alkaline metals

Take about 1 g of sodium nitrate into a test tube and fix it in a stand. Heat the test tube in a flame and examine the evaluation of oxygen.

4. Interaction of calcium with water

Take some distilled water into a porcelain dish and add some drops of phenolphtalein. Put a small piece of calcium into the cup (use pincers). Compare the rate of the evaluation of hydrogen with the one from experiment 1b.

5. Formation of carbonates

Fill 3 test tubes with 1 ml of solutions of calcium, strontium and barium salts respectively and add 1 ml of sodium carbonate solution into each test tube. Try to dissolve the formed precipitates in hydrochloric acid.

6. Formation of calcium and barium oxalates

Fill 2 test tubes with 1 ml of the solutions of calcium and barium salts respectively and add 1 ml of ammonium oxalate (NH₄)₂C₂O₄. Divide each precipitate into two parts and try to dissolve them in hydrochloric and acetic acids.

7. Formation of gypsum

Put 1-2 ml of a saturated solution of calcium chloride in a test tube and add 1-2 ml of 50% solution of sulfuric acid. Observe the formation of the crystals of gypsum.

QUESTIONS AND PROBLEMS

1. How does the value of the ionization potential changes with the change of the position of an element in the periodic table?

2. Which are the rules of storage and handling of alkaline and alkaline earth metals?

3. How are compounds of alkaline and alkaline earth metals are used in the medical practice?

4. Calculate pH of 0.01 M solution of sodium acetate.

5. Calculate the equilibrium constants of the reactions and explain why the precipitate of barium chromate can be dissolved in hydrochloric acid and can’t be dissolved in acetic acid.

Experiment 7 elements of iiia and iva groups

(P - ELEMENTS)

Boron and aluminum are elements of the IIIA group of the periodic table. Atomic radius of boron is 0.91Å and the one of aluminum is 1.43Å. This great difference affects chemical properties of these elements. Ionization potential of boron is greater than that of aluminum. Polarity of B-O chemical bond is small, so in solutions boron exists as BO₂ and BO₃³ ions (acidic properties). Al-O chemical bonds have a more polar character, so in solutions aluminum exists both as Al³⁺ and AlO₂ ions (amphoteric properties).

Salts of boric acid H₃BO₃ are metaborates (Ba(BO₂)₂) and tetraborates (Na₂B₄O₇ - borax).