1. John E McMurry and Robert C Fay CHEMISTRY Chapter 18 Hydrogen Oxygen and Water Chapter 18/1

2. Hydrogen Isotopes of Hydrogen Binary Hydrides Oxygen Preparation and uses of Oxygen Peroxides and Superoxides Hydrates

3. Chapter 18/3 Hydrogen H 2 (g) + Zn 2+ (aq)2H 1+ (aq) + Zn(s) In 1781 Cavendish demonstrated when hydrogen burned it formed water. The French chemist Lavoisier called the gas “hydrogen” which means “water former.” Henry Cavendish (1731-1810) in 1766 is credited with isolating hydrogen in its pure form:  Hydrogen is most abundant element in the universe  It is 9 th most abundant element on mass % basis on Earth.  It is colorless odorless and tasteless gas

4. Chapter 18/4 Isotopes of Hydrogen Three isotopes: 1.Hydrogen-1 (protium): 99.985% abundance 2.Hydrogen-2 (deuterium): 0.015% abundance 3.Hydrogen-3 (tritium): about 10 -16 % abundance H 2 1 H 3 1 H 1 1

5. Isotopes of Hydrogen

6. Chapter 18/6 Isotopes of Hydrogen Isotope Effects K w = 0.195 x 10 -14 D 3 O 1+ (aq) + OD 1- (aq)2D 2 O(l) K w = 1.01 x 10 -14 H 3 O 1+ (aq) + OH 1- (aq)2H 2 O(l) 2D 2 O(l)2D 2 (g) + O 2 (g) Electrolysis 2H 2 O(l)2H 2 (g) + O 2 (g) Electrolysis Slower Faster

7. Preparation and Uses of Hydrogen 2H 2 (g) + O 2 (g)2H 2 O(l)  H° = +572 kJ

8. Binary Hydrides

9. Chapter 18/9 Binary Hydrides Ionic Hydrides The hydride ion is a good proton acceptor (Brønsted-Lowry base):  H° = -181.5 kJ CaH 2 (s)Ca(s) + H 2 (g) 400 °C  H° = -112.6 kJ 2NaH(s)2Na(l) + H 2 (g) 400 °C Saltlike, high melting, white, crystalline compounds formed by the alkali metals and the heavier alkaline earth metals Ca, Sr, and Ba: 2H 2 (g) + Ca 2+ (aq) + 2OH 1- (aq)CaH 2 (s) + 2H 2 O(l)

10. Chapter 18/10 Binary Hydrides Covalent Hydrides Common hydrides of nonmetallic elements, such as diborane (B 2 H 6 ), methane (CH 4 ), ammonia (NH 3 ), water (H 2 O), and hydrogen halides (HX; X = F, Cl, Br, or I ). In general, their intermolecular forces are relatively weak so they exist as gases or volatile liquids at ordinary temperatures.

11. Chapter 18/11 Binary Hydrides Metallic Hydrides Formed by the reaction of the lanthanides and actinide metals and certain d-block transition metals with variable amounts of hydrogen with the general formula MH x. PdH x (s)Pd(s) + H 2 (g) 2 x Favored at lower temperature Favored at higher temperature

12. Chapter 18/12 Oxygen Priestly called the gas “dephlogisticated air.” Lavoisier called it “oxygen” which means “acid former.” Gaseous O 2 condenses at -183 °C to form a pale blue liquid and freezes at -219 to give a pale blue solid. Joseph Priestly and Karl Wilhelm Scheele are credited for isolating and characterizing oxygen between 1771 and 1774: 2Hg(l) + O 2 (g)2HgO(s) Heat

13. Chapter 18/13 Preparation and Uses of Oxygen 2H 2 O 2 (aq)2H 2 O(l) + O 2 (g) Catalyst Small amounts of oxygen can be generated in the lab: 2H 2 O(l)2H 2 (g) + O 2 (g) Electrolysis 2KCl(s) + 3O 2 (g)2KClO 3 (s) MnO 2 catalyst Heat Photosynthesis constantly replaces used oxygen: 6O 2 + C 6 H 12 O 6 6CO 2 + 6H 2 O h Glucose

14. Chapter 18/14 Oxides  Binary compounds in which oxygen is in:  -2 oxidation state are called oxides.  -1 oxidation state are called peroxides.  -1/2 oxidation state are called superoxides.

15. Chapter 18/15 Oxides

16. Peroxides and Superoxides When some of the group 1A and group 2A metals are heated in excess oxygen, they will form either peroxides, such as Na 2 O 2 and BaO 2, or superoxides, such as KO 2, RbO 2, and CsO 2.

17. Chapter 18/17 Peroxides and Superoxides O 2 (g) + 2K 1+ (aq) + HO 2 1- (s) +OH 1- (aq)KO 2 (s) + H 2 O(l) Superoxides can dissolve in water: 2Na 1+ (aq) + HO 2 1- (aq) + OH 1- (aq)Na 2 O 2 (s) + H 2 O(l) The peroxide ion is a basic anion: BaS 4 (s) + H 2 O 2 (aq)BaO 2 (s) + H 2 SO 4 (aq) Peroxides will react with strong acids:

18. Chapter 18/18 Hydrogen Peroxide Pure hydrogen peroxide freezes at 4 °C and is estimated to boil at 150 °C.

19. Chapter 18/19 Water

20. Chapter 18/20 Hydrates Compounds that absorb water from the air are hygroscopic and can be used as drying agents. CuSO 4 5H 2 O Hydrates: Solid compounds that contain water molecules. Mg(ClO 4 ) 2 6H 2 O AlCl 3 6H 2 O CoCl 2 6H 2 O(s)CoCl 2 (s) + 6H 2 O(l)