The Foundations of Chemistry

The primary industrial use of H 2 is in the synthesis of ammonia, a molecular hydride,

by the Haber process (Section 17-7). Most of the NH 3 is used in liquid form as a fertil-

izer (Figure 6-6) or to make other fertilizers, such as ammonium nitrate, NH 4 NO 3 , and

ammonium sulfate, (NH 4 ) 2 SO 4 :

catalysts

N 2 (g)3H 2 (g)88888888888888n2NH 3 (g)

heat, high pressure

Many of the molecular (nonmetal) hydrides are acidic;their aqueous solutions contain

hydrogen ions. These include HF, HCl, HBr, HI, H 2 S, H 2 Se, and H 2 Te.

EXAMPLE 6-6 Predicting Products of Reactions

Predict the products of the reactions involving the reactants shown. Write a balanced formula

unit equation for each.

heat

(a) H 2 (g)I 2 (g)888n

heat

(b) K(
)H 2 (g)888n

(c) NaH(s)H 2 O(
) (excess)88n

Plan

(a) Hydrogen reacts with the halogens (Group VIIA) to form hydrogen halides—in this

example, HI.

(b) Hydrogen reacts with active metals to produce hydrides—in this case, KH.

(c) Active metal hydrides react with water to produce a metal hydroxide and H 2.

Solution

heat

(a) H 2 (g)I 2 (g)888n2HI(g)

heat

(b) 2K(
)H 2 (g)888n2KH(s)

(c) NaH(s)H 2 O(
)88nNaOH(aq)H 2 (g)

Figure 6-5 Hydrogen, H 2 , burns
in an atmosphere of pure chlorine,
Cl 2 , to produce hydrogen chloride.

H 2 Cl 2 88n2HCl

254 CHAPTER 6: Chemical Periodicity

Figure 6-6 Ammonia may be applied directly to the soil as a fertilizer.

Remember that hydride ions, H
,
react with (reduce) water to produce
OH
ions and H 2 (g).