Chemical Reactivity of some representative elements 1. Magnesium and Aluminum a.

Question

Chemical Reactivity of some representative elements

1. Magnesium and Aluminum

a. Which metal reacts more rapidly with HCl?

Whiat is the gas that is evolved when Mg and Al react with HCl?

b. Reaction of metal ion with NaOH

c. Explain the differences in chemical behavior of the magnesium and aluminum hydroxides. Use chemical equations in your discussion.

2. Solubilities of Alkaline_Earth Cations

0.1M CaCl2

List the hydroxide salts in order of increasing solubility

List the sulfate salts in order of increasing solubility

What can you conclude about the general trend in solubilities of the Group 2A metal hydroxides and sulfates?

3. Sulfurous Acid and Sulfuric Acid

a. What does the litmus test indicate about the chemical stability of sulfurous acid?

b. What is the gas that is generated?

c. Write an equation for the decomposition of sulfurous acid

d. What does the litmus test indicate about the chemical stability of sulfuric acid?

e. What chemical property differentiates sulfurous acid from sulfuric acid?

5-10 drops of 6M HCl

Observation 6M NaOH Excess 6M NaOH Mg2+ (drops to precipitate) Al3+ (drops to precipitate)

Explanation / Answer

1. a. Magnesium is more reactive as compared to Aluminum. So, Magnesium will react at a faster rate with HCl than Aluminum.

     The gas liberated during raection of Aluminum or Magnesium with HCl is Hydrogen (H2).

b. Mg2+ on reaction with 6 M NaOH forms a white precipitate of Mg(OH)2 which remains unaltered upon addition of excess 6 M NaOH.

   Al3+ on reaction with 6 M NaOH forms a gelatinous precipitate of Al(OH)3 which gets soluble upon addition of excess 6 M NaOH as soluble Sodium Aluminate salt is formed.

     Al(OH)3 + NaOH = NaAlO2 + 2 H2O

The list of Hydroxide salts according to order of solubility is

     Ba(OH)2 > Sr(OH)2 > Ca(OH)2 > Mg(OH)2 > Be(OH)2 : The solubility increases down the group.

The list of Sulfate salts according to order of solubility is

     BeSO4 > MgSO4 > CaSO4 > SrSO4 > BaSO4 : The solubility decreases down the group.

The litmus test of Sulfurous acid indicates that the acidity of Sulfurous acid is transcient. This characteristics can be attributed to thermal decomposition of Sulfurous acid.

     H2SO3 = H2O + SO2

But same test with Sulfuric acid shows permanent red color of the red litmus paper which indicates the stability of sulfuric acid.

Na2SO3 reacts with concentrated HCl according to the following reaction:

     Na2SO3 + 2HCl = 2NaCl + SO2 + H2O

Na2SO4 does not react with HCl according to that fashion.

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