A Since ancient Roman times (or before), it has been known (in somewhat differen

Question

A Since ancient Roman times (or before), it has been known (in somewhat different terms) that sodium oxide and calcium oxide can be combined with Sit), to make glass. Class is not a stoichiometric compound, but we could think of it crudely as a mixture of Na_2SiO_3 + CaSiO_3 + SiO_2 Explain how the making of glass could be explained as an acid-base reaction. 2 lon-cydotron resonance experiments allow scientists to observe gas phase reactions of ions. In one study, (Wyatt, R.M. Holtz, D.; McMahon, I B.; Beauchamp. J.L. Client., 1974, 1.1, 1511-1517) it was reported that the following reaction tends to go forward: Which is the stronger add, PH, or AsH? Is this in agreement with the general trends for binary acids? What the usual rationalization tor this trend? What might complicate the picture from this rationalization?

Explanation / Answer

Solution 1:

Na2O and CaO are basic oxides and SiO2 is an acidic oxide

Thus, there exists an acid base reaction between Na2O and SiO2 to form Na2SiO3.

i.e., Na2O + SiO2 à Na2SiO3.

(we can also explain this reaction by using Lewis theory of acid basesas follows;

                Na2O à 2 Na+ + O – 2

                O – 2 (electron pair donor:base)+ SiO2 (electron pair acceptor: acid)à SiO3– 2

                2Na+ + SiO3– 2 à Na2SiO3.

Similarly, CaO + SiO2 à CaSiO3.

Solution 2:

PH2– 1 + AsH3 à PH3 + AsH2– 1

In this reaction PH2– 1 is accepting proton from AsH3 , thus PH2- is a base and AsH3 is an acid according to Lowry and Bronsted theory.

According to Lowry and Bronsted theory, strong acid produced a conjugate weak base and weak base produces a conjugate strong acid

PH3 is a weak base with Ka = 10 – 28 and it is produced from PH2-1, thus PH2-1 is a strong acid.

As we know AsH3 is a weak base and thus its conjugate acid AsH2– 1 is strong acid.

Conclusions:

PH2– 1 - strong acid

PH3 – weak base

AsH3 – weak base

AsH2– 1 - Strong acid

PH2– 1 acting as a strong acid is un-usual trend here. However, this is a active species produced by liquid ammonia (as solvent) and Na metal at – 20°C upon reaction with phosphine (PH3).

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