Chapter21ISM

Chapter21ISM - CHAPTER 21 NONMETALLIC ELEMENTS AND THEIR...

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CHAPTER 21 NONMETALLIC ELEMENTS AND THEIR COMPOUNDS Problem Categories Conceptual : 21.14, 21.34, 21.44, 21.46, 21.53, 21.58, 21.65, 21.67, 21.69, 21.73, 21.74, 21.89, 21.94, 21.95, 21.97, 21.98, 21.101. Descriptive : 21.11, 21.12, 21.13, 21.15, 21.17, 21.18, 21.25, 21.27, 21.28, 21.29, 21.30, 21.31, 21.32, 21.33, 21.39, 21.40, 21.41, 21.42, 21.43, 21.45, 21.47, 21.48, 21.49, 21.55, 21.56, 21.57, 21.71, 21.75, 21.77, 21.78, 21.81, 21.82, 21.83, 21.86, 21.87, 21.90, 21.91, 21.92, 21.93, 21.96, 21.99. Environmental : 21.66. Industrial : 21.52, 21.70, 21.100. Difficulty Level Easy : 21.25, 21.26, 21.27, 21.29, 21.34, 21.41, 21.46, 21.47, 21.49, 21.50, 21.52, 21.53, 21.55, 21.56, 21.58, 21.65, 21.68, 21.73, 21.85, 21.86, 21.90, 21.94, 21.97. Medium : 21.11, 21.12, 21.13, 21.14, 21.15, 21.16, 21.17, 21.18, 21.28, 21.30, 21.31, 21.32, 21.39, 21.40, 21.42, 21.44, 21.51, 21.54, 21.66, 21.67, 21.69, 21.70, 21.72, 21.74, 21.75, 21.77, 21.78, 21.81, 21.84, 21.87, 21.88, 21.89, 21.91, 21.92, 21.95, 21.98, 21.99, 21.100, 21.101, 21.104. Difficult : 21.33, 21.43, 21.45, 21.48, 21.57, 21.71, 21.76, 21.82, 21.83, 21.93, 21.96, 21.102, 21.103, 21.105, 21.106. 21.11 Element number 17 is the halogen, chlorine. Since it is a nonmetal, chlorine will form the molecular compound HCl. Element 20 is the alkaline earth metal calcium which will form an ionic hydride, CaH 2 . A water solution of HCl is called hydrochloric acid. Calcium hydride will react according to the equation (see Section 21.2 of the text). CaH 2 ( s ) + 2H 2 O( l ) Ca(OH) 2 ( aq ) + 2H 2 ( g ) 21.12 (a) Hydrogen reacts with alkali metals to form ionic hydrides: 2Na( s ) + H 2 ( g ) 2NaH( s ) The oxidation number of hydrogen drops from 0 to 1 in this reaction. (b) Hydrogen reacts with oxygen (combustion) to form water: 2H 2 ( g ) + O 2 ( g ) 2H 2 O( l ) The oxidation number of hydrogen increases from 0 to + 1 in this reaction. 21.13 NaH: Ionic compound. It reacts with water as follows: NaH( s ) + H 2 O( l ) NaOH( aq ) + H 2 ( g ) CaH 2 : Ionic compound: It reacts with water as follows: CaH 2 ( g ) + 2H 2 O( l ) Ca(OH) 2 ( s ) + 2H 2 ( g ) CH 4 : Covalent compound. Unreactive. It burns in air or oxygen: CH 4 ( g ) + 2O 2 ( g ) CO 2 ( g ) + 2H 2 O( l )
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CHAPTER 21: NONMETALLIC ELEMENTS AND THEIR COMPOUNDS 622 NH 3 : Covalent compound. It is a weak base in water: NH 3 ( aq ) + H 2 O( l ) U NH 4 + ( aq ) + OH ( aq ) H 2 O: Covalent compound. It forms strong intermolecular hydrogen bonds. It is a good solvent for both ionic compounds and substances capable of forming hydrogen bonds. HCl: Covalent compound (polar). It acts as a strong acid in water: HCl( g ) + H 2 O( l ) H 3 O + ( aq ) + Cl ( aq ) 21.14 Hydrogen forms an interstitial hydride with palladium, which behaves almost like a solution of hydrogen atoms in the metal. At elevated temperatures hydrogen atoms can pass through solid palladium; other substances cannot. 21.15 The equation is: CaH 2 ( s ) + 2H 2 O( l ) Ca(OH) 2 ( aq ) + 2H 2 ( g ) First, let’s calculate the moles of H 2 using the ideal gas law. 22 1atm 746 mmHg (26.4 L) 760 mmHg mol H 1.08 mol H (0.0821 L atm/mol K)(293 K) ⎛⎞ × ⎜⎟ ⎝⎠ == ⋅⋅ Now, we can calculate the mass of CaH 2 using the correct mole ratio from the balanced equation. 2 2 1molCaH 42.10 g 1.08 mol H 2mo lH 1mo lCaH =×× = Mass CaH 22.7 g CaH 21.16 The number of moles of deuterium gas is: (0.90 atm)(2.0 L) 0.074 mol (0.0821 L atm/K mol)(298 K) = PV n RT If the abundance of deuterium is 0.015 percent, the number of moles of water must be: 2 2 2 100% H O 0.074 mol D 4.9 10 mol H O 0.015% D ×= × At a recovery of 80 percent the amount of water needed is: 2 2 4.9 10 mol H O 0.01802 kg H O 0.80 1.0 mol H O × 2 11 kg H O 21.17 According to Table 19.1 of the text, H 2 can reduce Cu 2 + , but not Na + . (How can you tell?) The reaction is: CuO( s ) + H 2 ( g ) Cu( s ) + H 2 O( l ) 21.18 (a) H 2 + Cl 2 2HCl (b) 3H 2 + N 2 2NH 3 (c) 2Li + H 2 2LiH LiH + H 2 O LiOH + H 2
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CHAPTER 21: NONMETALLIC ELEMENTS AND THEIR COMPOUNDS 623 21.25 The reaction can be represented: The lone pair on the hydroxide oxygen becomes a new carbon-oxygen bond.
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This note was uploaded on 02/08/2012 for the course CHEM 161 taught by Professor Shaklovich during the Spring '10 term at Harvard.

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Chapter21ISM - CHAPTER 21 NONMETALLIC ELEMENTS AND THEIR...

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