Gas Stoichiometry Gas Stoichiometry We have looked at

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Gas Stoichiometry

Gas Stoichiometry

Gas Stoichiometry • We have looked at stoichiometry: 1) using masses & molar masses,

Gas Stoichiometry • We have looked at stoichiometry: 1) using masses & molar masses, & 2) concentrations. • We can use stoichiometry for gas reactions. • As before, we need to consider mole ratios when examining reactions quantitatively. molar mass of x mole ratio from molar mass of y balanced equation PV = n. RT grams (x) moles (y) grams (y) P, V, T (x) P, V, T (y) • At times you will be able to use 22. 4 L/mol at STP and 24. 8 L/mol at SATP as shortcuts.

Sample problem 1 CH 4 burns in O 2, producing CO 2 and H

Sample problem 1 CH 4 burns in O 2, producing CO 2 and H 2 O(g). A 1. 22 L CH 4 cylinder, at 15°C, registers a pressure of 328 k. Pa. a) What volume of O 2 at SATP will be required to react completely with all of the CH 4? First: CH 4(g) + 2 O 2(g) CO 2(g) + 2 H 2 O(g) PV = n. RT P = 328 k. Pa, V = 1. 22 L, T = 288 K (328 k. Pa)(1. 22 L) = n = 0. 167 mol (8. 31 k. Pa • L/K • mol)(288 K) # mol O 2= 0. 167 mol CH 4 x 2 mol O 2 = 0. 334 mol 1 mol CH 4 PV = n. RT P= 100 k. Pa, n= 0. 334 mol, T= 298 K (0. 334 mol)(8. 31 k. Pa • L/K • mol)(298 K) =V = 8. 28 L (100 k. Pa) or # L = 0. 334 mol x 24. 8 L/mol =

Sample problem 1 continued CH 4(g) + 2 O 2(g) CO 2(g) + 2

Sample problem 1 continued CH 4(g) + 2 O 2(g) CO 2(g) + 2 H 2 O(g) b) How many grams of H 2 O(g) are produced? mol H 2 O 18. 02 g H 2 O= 6. 02 g # g H 2 O= 0. 167 mol CHx 2 x 4 1 mol CH 41 mol H 2 O c) What volume of CO 2 (at STP) is produced if only 2. 15 g of the CH 4 was burned? 1 mol CH 41 mol CO 2= 0. 134 # mol CO = 2. 15 g CH 2 x 4 x 16. 05 g CH 14 mol CH 4 mol COT 2 = PV = n. RT P = 101. 3 k. Pa, n = 0. 134 mol, (0. 134273 mol)(8. 31 K = V = 3. 00 L (101. 3 KPa) k. Pa • L/K • mol )(273 K) CO 2 or # L = 0. 134 mol x 22. 4 L/mol =

Sample problem 2 Ammonia (NH 3) gas can be synthesized from nitrogen gas +

Sample problem 2 Ammonia (NH 3) gas can be synthesized from nitrogen gas + hydrogen gas. What volume of ammonia at 450 k. Pa and 80°C can be obtained from the complete reaction of 7. 5 kg hydrogen? First we need a balanced equation: N 2(g) + 3 H 2(g) 2 NH 3(g) 1 mol H 2 2 mol NH 3= 2475 mol # mol NH 7500 = g H 3 x 2. 02 g H 2 3 mol H 2 PV = n. RT P = 450 k. Pa, n = 2475 mol, T = 353 K (2475 mol)(8. 31)(353 K) = V = 16 135 L (450 KPa) NH 3

Sample problem 3 Hydrogen gas (and Na. OH) is produced when sodium metal is

Sample problem 3 Hydrogen gas (and Na. OH) is produced when sodium metal is added to water. What mass of Na is needed to produce 20. 0 L of H 2 at STP? First we need a balanced equation: 2 Na(s) + 2 H 2 O(l) H 2(g) + 2 Na. OH(aq) PV = n. RT P= 101. 3 k. Pa, V= 20. 0 L, T= 273 K (101. 3 k. Pa)(20. 0 L) = n = 0. 893 mol H 2 (8. 31 k. Pa • L/K • mol)(273 K) or # mol = 20. 0 L x 1 mol / 22. 4 L = 0. 893 mol 2 mol Na 22. 99 g Na # g Na= 0. 893 mol Hx x 2 = 41. 1 g Na 1 mol H 2 1 mol Na

Assignment 1. What volume of oxygen at STP is needed to completely burn 15

Assignment 1. What volume of oxygen at STP is needed to completely burn 15 g of methanol (CH 3 OH) in a fondue burner? (CO 2 + H 2 O are products) 2. When sodium chloride is heated to 800°C it can be electrolytically decomposed into Na metal & chlorine (Cl 2) gas. What volume of chlorine gas is produced (at 800°C and 100 k. Pa) if 105 g of Na is also produced? 3. What mass of propane (C 3 H 8) can be burned using 100 L of air at SATP? Note: 1) air is 20% O 2, so 100 L of air holds 20 L O 2, 2) CO 2 and H 2 O are the products of this reaction.

4. A 5. 0 L tank holds 13 atm of propane (C 3 H

4. A 5. 0 L tank holds 13 atm of propane (C 3 H 8) at 10°C. What volume of O 2 at 10°C & 103 k. Pa will be required to react with all of the propane? 5. Nitroglycerin explodes according to: 4 C 3 H 5(NO 3)3(l) 12 CO 2(g) + 6 N 2(g) + 10 H 2 O(g) + O 2(g) a) Calculate the volume, at STP, of each product formed by the reaction of 100 g of C 3 H 5(NO 3)3. b) 200 g of C 3 H 5(NO 3)3 is ignited (and completely decomposes) in an otherwise empty 50 L gas cylinder. What will the pressure in the cylinder be if the temperature stabilizes at 220°C?

Answers 1. 3 O 2(g) + 2 CH 3 OH(l) 2 CO 2(g) +

Answers 1. 3 O 2(g) + 2 CH 3 OH(l) 2 CO 2(g) + 4 H 2 O(g) # L O 2= 15 g x 1 mol CH 3 OHx 3 mol O 2 x 22. 4 L O 2 CH 3 OH 32. 05 g CH 3 OH 2 mol CH 3 OH 1 mol O 2 = 15. 7 L O 2 2. 2 Na. Cl(l) 2 Na(l) + Cl 2(g) 1 mol Na 1 mol Cl 2= 2. 284 mol C # mol Cl 105 = g Na x x 2 22. 99 g Na 2 mol Na PV = n. RT P = 100 k. Pa, n = 2. 284 mol, T = 1073 K K) = V = 204 L Cl (2. 284 mol)(8. 31)(1073 2 (100 KPa)

3. C 3 H 8(g) + 5 O 2(g) 3 CO 2(g) + 4

3. C 3 H 8(g) + 5 O 2(g) 3 CO 2(g) + 4 H 2 O(g) g C 3 H 8 #g 20 L O 2 x 1 mol C 3 H 844. 11 x 24. 8 L O 2 5 mol O 2 1 mol C 3 H 8= = 7. 1 g C 3 H 8 4. C 3 H 8(g) + 5 O 2(g) 3 CO 2(g) + 4 H 2 O(g) PV = n. RT n = (1317 k. Pa)(5. 0 = 2. 8 mol L) K) (8. 31)(283 C 3 H 8 # mol O 2= 2. 8 mol x 5 mol O 2 = 14 mol C 3 H 8 1 mol C 3 H 8 O 2 PV = n. RT P = 103 k. Pa, n = 14 mol, T = 283 K (14 mol)(8. 31)(283 = V = 320 L O 2 (103 K) KPa)

5. # mol C 3 H 5100 (NO 3 g)3= x 1 mol C

5. # mol C 3 H 5100 (NO 3 g)3= x 1 mol C 3 H 5(NO 3)3= 0. 4403 mol C 3 H 5(NO 3)3227. 11 g C 3 H 5(NO 3)3 12 mol CO 22. 4 L 0. 4403 mol = 29. 6 2 # L CO 2= x x C 3 H 5(NO 34 mol C 3 H 5(NO 3)13 mol L )3 CO 2 6 mol N 22. 4 L 0. 4403 mol = 14. 8 2 # L N 2= x x C 3 H 5(NO 34 mol C 3 H 5(NO 3)13 mol L N 2 )3 10 mol H O 22. 4 L 0. 4403 mol = 24. 7 2 # L H 2 O= x x C 3 H 5(NO 34 mol C 3 H 5(NO 3)13 mol L )3 H 2 O 1 mol O 22. 4 L 0. 4403 mol = 2. 47 2 # L O 2= x x C 3 H 5(NO 34 mol C 3 H 5(NO 3)13 mol L O 2 )

5. # mol C 3 H 5200 (NO 3 g)3= x 1 mol C

5. # mol C 3 H 5200 (NO 3 g)3= x 1 mol C 3 H 5(NO 3)3= 0. 8806 mol C 3 H 5(NO 3)3227. 11 g C 3 H 5(NO 3)3 # mol all gases= 29 mol gases = 6. 385 0. 8806 mol x C 3 H 5(NO 3)3 4 mol C 3 H 5(NO 3)3 mol all gases PV = n. RT V = 50 L, n = 6. 385 mol, T = 493 K (6. 385 mol)(8. 31)(493 K) = P = 523 k. Pa (50 L) For more lessons, visit www. chalkbored. com