# MASS-VOLUME AND VOLUME-VOLUME PROBLEMS AT NON-STP CONDITIONS

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```					                    Gas Stoichiometry at NON-STP CONDITIONS

Name ________________________________                                      Date______________________
Period ________

1. Potassium chlorate decomposes with heat into potassium chloride and oxygen gas. If 7.400 grams of
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potassium chlorate are decomposed and the oxygen gas is collected over water at 22 C and
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740.0 torr, how many milliliters of oxygen gas were collected? The vapor pressure of water at 22
C is 19.8 torr. (2315 ml)

(work this problem first using a mass-volume problem to find what volume of oxygen is produced
at STP and then do a combined gas law problem to correct the oxygen gas to conditions
specified in the problem)

(work the same problem again doing a mass-mole problem first to find out how many MOLES of
oxygen are produced and then use PV=nRT to find the volume of this many moles of oxygen
under the conditions specified in the problem)

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2. If 3.5 liters of hydrogen gas at 27 C and 730 torr are reacted with 2.5 liters of oxygen gas at 22 C and
750 torr, how many grams of water will be produced? (2.46 g)

(b) What is the limiting reactant (hydrogen)

3. Would an 850-milliliter flask be large enough to collect al the oxygen which can be produced and
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collected OVER WATER at 35 C and 700 torr when 2.04 grams of hydrogen peroxide (H2O2 ) are
decomposed in the presence of a catalyst into water and oxygen gas? The vapor pressure of
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water at 35 C is 42.2 torr. (no, volume of oxygen collected under these conditions is 876 ml)
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4. How many liters of hydrogen gas can be collected over water at 66 C and 730 torr when 67.0 grams of
zinc reacts with 72.0 grams of phosphoric acid which is 53% H3PO4 ? The vapor pressure of
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water at 66 C is 196.1 torr. (23.2 liters)

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5. If 17.4 liters of methane (CH4) at 30 C and 800 torr are reacted with 32.0 liters of oxygen at 20 C and
700 torr in a complete combustion reaction, how many grams of water will be formed (22.1 g
water)

(work this problem using the combined gas law to change EACH of the reactants to STP, decide
which is the limiting reactant and work a volume-mass problem to see how much water is
formed.)

(work this same problem again using PV=nRT to find the moles of each reactant, decide which is
the limiting reactant and then do a mass-mass problem to see how much water is formed)

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6. If 70.2 liters of hydrogen gas at 600 torr and 60 C are reacted with 36.0 grams of oxygen, how many
grams of water are produced? (36.5 g)

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7. If 47.2 liters of nitrogen gas at 20 C and 700 torr are reacted with 100 liters of hydrogen gas at 25oC
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and 800 torr, how many liters of ammonia will form and be collected at 750 torr and 18 C? (69.4
liters)

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8. How many liters of hydrogen gas at 600 torr and 20 C are needed to completely react with 45.7 liters
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of oxygen at 850 torr and 30 C in the synthesis of liquid water? (125.2 liters)

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