Reference observations of the reactivity of the cited metals in water and/or aci

Question

Reference observations of the reactivity of the cited metals in water and/or acid to explain the following: A high dietary intake of dissolved A1 is associated with development of neurological disorders. Cooks are warned to not prepare highly acidic foods like chile and spaghetti sauce in aluminum pans. Dietary intake of Ca is important for good health. Would it be practical to manufacture cookware using calcium, rather than aluminum? Apply the analysis of observed reaction results to answer the following: Zn is less active than Mg. Write equations describing the reactions which occur when: Zn reacts with a 0.5M magnesium chloride, MgCl_2 Mg reacts with 0.5M zinc chloride, ZnCl_2

Explanation / Answer

7 a).

Dissolved Aluminium is Al3+ ions.and not Al atoms Al3+ is harmful.

Chile and Sphagetti sauce contains vinegar which is dilue actic acid solution

Al metal reacts with acetic acid producing Aluminium acetate salt and Hydrogen gas

2Al + 6 CH3COOH = 2(CH3COO)3Al + 3 H2

That is why cooks are warned to not prepare highly acidic foods in Al pans.

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7 b)

Ca is a soft metal.

It is slowly acted upon by air and burns in it on heating to form a mixture of oxide and nitride.

2Ca +O2 = 2CaO

3Ca + N2 = Ca3N2

It decomposes water with the liberation of H2 gas

Ca +2H2O =Ca(OH)2 + H2

For these reasons, it is not practical to manufacure cookware using Ca

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8

Elements with a tendency to lose electron(s) are called electropositive elements. .

The greater the tendency to lose electrons, the greater the eectropositive character of the element

A MORE ELECTROPOSITIVE ELEMENT CAN DISPLACE A LESS ELECTROPOSITIVE ELEMENT FROM ITS SALT SOLUTION.

BUT A LESS ELECTROPOSITIVE ELEMENT CANNOT DISPLACE A MORE ELECTROPOSITIVE ELEMENT FROM ITS SALT SOLUTION.

Zn is less active ie less electropositive than Mg.Hence Zn cannot displace Mg from its salt solution .So there will be no reaction between Zn and MgCl2 solution.

On the other hand ,Mg is more active ie more electropositive than Zn .Hence Mg can displace Zn from its salt solution

So Mg will react with ZnCl2 solution producing MgCl2 and depositing Zn

ZnCl2 (aq) + Mg(s) = MgCl2(aq) + Zn(s)

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