WS6_key - Chem 142 Name _ Worksheet 6: Gases Ideal Gas Law:...

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Chem 142 Summer 2011 Page 1 of 9 Name ________________________________________ Section ________________ Worksheet 6: Gases Ideal Gas Law: PV=nRT 1. The major industrial source of hydrogen gas is the reaction of methane with water at high temperatures (800-1000 ° C) and pressures (10-50 atm) in the presence of the metallic catalyst (often nickel): 1 CH 4 (g) + 1 H 2 O (g) 1 CO (g) + 3 H 2 (g) 2.00 L of CH 4 (g) and 3.00 L of H 2 O (g) at 25.0 ° C and 1.00 atm are placed in a 1.00 L rigid reaction vessel and heated to 1000.0 ° C and held constant. a. Do you expect the new pressure or be higher or lower? What is the pressure within the reaction vessel? Is this pressure sufficient for the reaction to proceed? PV T = nR = constant ! P 1 V 1 T 1 = P 2 V 2 T 2 Combined Gas Law P 2 = P 1 V 1 T 1 ! T 2 V 2 = 1 atm ! (2.00 L + 3.00 L ) 298 K ! 1273 K 1.00 L = 21.4 atm Yes, the pressure is sufficient. b. Assuming the reaction goes to completion, how many moles of H 2 (g) will be produced by this reaction? 1.00 atm ( ) ! 2.00 L ( ) 0.08206 L " atm mol " K # $ % ( ! 298 K ( ) = 0.0818 mol CH 4 1.00 atm ( ) ! 3.00 L ( ) 0.08206 L " atm mol " K # $ % ( ! 298 K ( ) = 0.123 mol H 2 O 1:1 ratio means that CH 4 is the limiting reagent. 0.0818 mol CH 4 ! 3 mol H 2 1 mol CH 4 = 0.245 mol H 2
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Chem 142 Summer 2011 Page 2 of 9 c. What will the partial pressure of each gas remaining in the vessel be? What is the total pressure within the reaction vessel? Partial pressure of H 2 P H 2 = 0.245 mol ( ) ! 0.08206 L " atm mol " K # $ % ( ! 1273 K ( ) 1.00 L ( ) = 25.6 atm Partial pressure of CO 0.0818 mol CH 4 ! 1 mol CO 1 mol CH 4 = 0.0818 mol CO P CO = 0.0818 mol ( ) ! 0.08206 L " atm mol " K # $ % ( ! 1273 K ( ) 1.00 L ( ) = 8.55 atm Partial pressure of excess H 2 O 0.123 mol H 2 O initially ! 0.0818 mol H 2 O used = 0.0412 mol H 2 O excess P H 2 O = 0.0412 mol ( ) ! 0.08206 L " atm mol " K # $ % ( ! 1273 K ( ) 1.00 L ( ) = 4.30 atm Total pressure is sum of the partial pressures P total = P H 2 O + P CO + P H 2 = 25.6 atm + 8.55 atm + 4.30 atm = 38.5 atm 2. Ammonia, a very important fertilizer and a starting material for the industrial synthesis of nitric acid, is made by combining nitrogen from the air with hydrogen according to the equation: 1 N 2 (g) + 3 H 2 (g) 2 NH 3 (g) This reaction (the Haber process) for manufacturing ammonia is carried out at a pressure of about 250 atm and a temperature of approximately 400 ° C. The H
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This note was uploaded on 01/19/2012 for the course CHEM 142A taught by Professor Campbell during the Summer '11 term at University of Washington.

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WS6_key - Chem 142 Name _ Worksheet 6: Gases Ideal Gas Law:...

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