7. Gases

Gas Stoichiometry

Gas Stoichiometry for Gases at STP

A mixture of CO(g) and O2(g) in a 1.0-L container at 1.0 * 103 K
has a total pressure of 2.2 atm. After some time, the total pressure
falls to 1.9 atm as the result of the formation of CO2. Determine
the mass (in grams) of CO2 that forms.

When 10.0 g of a mixture of Ca1ClO322 and 
Ca1ClO22 is heated to 700 °C in a 10.0-L vessel, both compounds 
decompose, forming O21g2 and CaCl21s2. The final 
pressure inside the vessel is 1.00 atm. 
(b) What is the mass of each compound in the original 
mixture?

Ammonium nitrate can decompose explosively when heated 
according to the equation 
2 NH4NO31s2¡2 N21g2 + 4 H2O1g2 + O21g2 
How many liters of gas would be formed at 450 °C and 
1.00 atm pressure by explosion of 450 g of NH4NO3?

Acetylene gas, C2H21g2, can be prepared by the reaction of
calcium carbide with water:
CaC21s2 + 2 H2O1l2¡Ca1OH221aq2 + C2H21g2
Calculate the volume of C2H2 that is collected over water at
23 °C by reaction of 1.524 g of CaC2 if the total pressure of
the gas is 100.4 kPa. (The vapor pressure of water is tabulated
in Appendix B.)

During a certain time period, 4.0 million tons of SO2 were 
released into the atmosphere and subsequently oxidized 
to SO3. As explained in the Inquiry, the acid rain produced 
when the SO3 dissolves in water can damage marble 
statues: 
CaCO31s2 + H2SO41aq2S CaSO41aq2 + CO21g2 
+ H2O1l2 
(b) How many liters of CO2 gas at 20 °C and 735 mm Hg 
is produced as a byproduct?.

Baking soda (sodium bicarbonate, NaHCO3) reacts with 
acids in foods to form carbonic acid 1H2CO32, which in 
turn decomposes to water and carbon dioxide gas. In a 
cake batter, the CO21g2 forms bubbles and causes the cake 
to rise. (c) If 1/2 teaspoon 
of baking soda is indeed completely neutralized by the 
lactic acid in sour milk, calculate the volume of carbon dioxide 
gas that would be produced at 1 atm pressure, in an 
oven set to 350 F.

A 6.53-g sample of a mixture of magnesium carbonate
and calcium carbonate is treated with excess
hydrochloric acid. The resulting reaction produces 1.72 L
of carbon dioxide gas at 28 °C and 99.06 kPa pressure.
(c) Assuming that the reactions are complete, calculate
the percentage by mass of magnesium carbonate in the
mixture.

Magnesium can be used as a “getter” in evacuated enclosures
to react with the last traces of oxygen. (The magnesium is
usually heated by passing an electric current through a wire
or ribbon of the metal.) If an enclosure of 5.67 L has a partial
pressure of O2 of 7.066 mPa at 30 °C, what mass of magnesium
will react according to the following equation?
2 Mg1s2 + O21g2¡2 MgO1s2

Consider the chemical reaction:
2 H2O(l )¡2 H2( g) + O2( g)
What mass of H2O is required to form 1.4 L of O2 at a temperature
of 315 K and a pressure of 0.957 atm?

A mixture of CS21g2 and excess O21g2 is placed in a 10.0-L 
reaction vessel at 100.0 °C and a pressure of 3.00 atm. 
A spark causes the CS2 to ignite, burning it completely, 
according to the equation 
CS21g2 + 3 O21g2¡CO21g2 + 2 SO21g2 
After reaction, the temperature returns to 100.0 °C, and 
the mixture of product gases (CO2, SO2, and unreacted O2) 
is found to have a pressure of 2.40 atm. What is the partial 
pressure of each gas in the product mixture?

The oxidation of phosphorus can be represented by the following equation: &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp;P4 (s) &nbsp;+ &nbsp;5 O2 (g) → 2 P2O5 (g) If 1.85 L of diphosphorus pentoxide form at a temperature of 50.0 ºC and 1.12 atm, what is the mass (in g) of phosphorus that reacted?

Hydrogen gas can be prepared by reaction of zinc metal
with aqueous HCl:
Zn1s2 + 2 HCl1aq2¡ZnCl21aq2 + H21g2
(a) How many liters of H2 would be formed at 742 mm Hg and 15 °C if 25.5 g of zinc was allowed to react?

A 4.00-g sample of a mixture of CaO and BaO is placed in a
1.00-L vessel containing CO2 gas at a pressure of 97.33 kPa
and a temperature of 25 °C. The CO2 reacts with the CaO
and BaO, forming CaCO3 and BaCO3. When the reaction
is complete, the pressure of the remaining CO2 is 20.0 kPa.
(b) Calculate the mass percentage of CaO in the mixture.

CH3OH can be synthesized by the reaction:
CO( g) + 2 H2( g)¡CH3OH( g)
What volume of H2 gas (in L), at 748 mmHg and 86 °C, is required
to synthesize 25.8 g CH3OH? How many liters of CO gas, 
measured under the same conditions, are required?

The hydrogen gas formed in a chemical reaction is collected
over water at 30.0 °C at a total pressure of 732 mmHg. What is
the partial pressure of the hydrogen gas collected in this way? If
the total volume of gas collected is 722 mL, what mass of hydrogen
gas is collected?

Consider the reaction:
2 Ag2O(s)¡4 Ag(s) + O2( g)
If this reaction produces 15.8 g of Ag(s), what total volume of gas
can be collected over water at a temperature of 25 °C and a total
pressure of 752 mmHg?

The zinc in a copper-plated penny will dissolve in hydrochloric
acid if the copper coating is filed down in several spots (so that the
hydrochloric acid can get to the zinc). The reaction between the
acid and the zinc is 2 H+ (aq) + Zn(s)¡ H2( g) + Zn2 + (aq).
When the zinc in a certain penny dissolves, the total volume of
gas collected over water at 25 °C is 0.951 L at a total pressure of
748 mmHg. What mass of hydrogen gas is collected?

Ammonium nitrate decomposes explosively upon heating
according
to the balanced equation:
2 NH4NO3(s)¡2 N2( g) + O2( g) + 4 H2O( g)
Calculate the total volume of gas (at 125 °C and 748 mmHg) produced
by the complete decomposition of 1.55 kg of ammonium
nitrate.

Gas Stoichiometry: Equations Part 1

Carbon monoxide gas reacts with hydrogen gas to form
methanol.
CO( g) + 2 H2( g)¡CH3OH( g)
A 1.50-L reaction vessel, initially at 305 K, contains carbon monoxide
gas at a partial pressure of 232 mmHg and hydrogen gas at
a partial pressure of 397 mmHg. Identify the limiting reactant. Determine the theoretical yield of methanol in grams.

Natural gas is very abundant in many Middle Eastern oil
fields. However, the costs of shipping the gas to markets in
other parts of the world are high because it is necessary to
liquefy the gas, which is mainly methane and has a boiling
point at atmospheric pressure of -164 °C. One possible
strategy is to oxidize the methane to methanol, CH3OH,
which has a boiling point of 65 °C and can therefore be
shipped more readily. Suppose that 3.03 * 108 m3 of methane
at atmospheric pressure and 25 °C is oxidized to methanol.
What volume of methanol is formed if the density
of CH3OH is 0.791 g>mL?

Ozone is depleted in the stratosphere by chlorine from CF3Cl
according to this set of equations:
CF3Cl + UV light¡CF3 + Cl
Cl + O3¡ClO + O2
O3 + UV light¡O2 + O
ClO + O¡Cl + O2
What total volume of ozone at a pressure of 25.0 mmHg and a
temperature of 225 K is destroyed when all of the chlorine from
15.0 g of CF3 Cl goes through 10 cycles of the given reactions?

Chlorine gas was first prepared in 1774 by the oxidation of
NaCl with MnO2:
2 NaCl1s2 + 2 H2SO41l2 + MnO21s2¡
Na2SO41s2 + MnSO41s2 + 2 H2O1g2 + Cl21g2
Assume that the gas produced is saturated with water vapor
at a partial pressure of 28.7 mm Hg and that it has a volume
of 0.597 L at 27 °C and 755 mm Hg pressure.
(b) How many grams of NaCl were used in the experiment,
assuming complete reaction?

Ammonia and hydrogen chloride react to form solid
ammonium chloride:
NH31g2 + HCl1g2¡NH4Cl1s2
Two 2.00-L flasks at 25 °C are connected by a valve,
as shown in the drawing. One flask contains 5.00 g
of NH31g2, and the other contains 5.00 g of HCl(g). When
the valve is opened, the gases react until one is completely
consumed. (b) What will be the final pressure
of the system after the reaction is complete? (Neglect
the volume of the ammonium chloride formed.) <img src="https://lightcat-files.s3.amazonaws.com/problem_images/8b7d934de3618efe-1660661544336.jpg" alt="" />

A group 3A metal has a density of 2.70 g>cm3 and a cubic unit cell with an edge length of 404 pm. Reaction of a 1.07 cm3 chunk of the metal with an excess of hydrochloric acid gives a colorless gas that occupies 4.00 L at 23.0 °C and a pressure of 740 mm Hg.
(a) Identify the metal.

Hydrogen gas can be prepared by reaction of zinc metal 
with aqueous HCl: 
Zn1s2 + 2 HCl1aq2¡ZnCl21aq2 + H21g2 
(b) How many grams of zinc would you start with if you 
wanted to prepare 5.00 L of H2 at 350 mm Hg and 30.0 °C?

The metabolic breakdown of glucose (C6H12O6) (MW:180.156 g/mol) is given by the following equation: C6H12O6 (s) &nbsp;+ &nbsp;6 O2 (g) → 6 CO2 (g) &nbsp;+ &nbsp;6 H2O (l) Calculate the volume (in mL) of CO2 produced at 34°C and 1728.9 torr when 231.88 g glucose is used up in the reaction.

A catalytic converter in an automobile uses a palladium or platinum
catalyst (a substance that increases the rate of a reaction
without being consumed by the reaction) to convert carbon
monoxide gas to carbon dioxide according to the reaction:
2 CO( g) + O2( g)¡2 CO2( g)
A chemist researching the effectiveness of a new catalyst combines
a 2.0:1.0 mole ratio mixture of carbon monoxide and oxygen
gas (respectively) over the catalyst in a 2.45-L flask at a
total pressure of 745 torr and a temperature of 552 °C. When
the reaction is complete, the pressure in the flask has dropped
to 552 torr. What percentage of the carbon monoxide was converted
to carbon dioxide?

Step by Step Gas Stoichiometry - Final Exam Review

Assume that an exhaled breath of air consists of 
74.8% N2, 15.3% O2, 3.7% CO2, and 6.2% water vapor. 
(c) How many grams of glucose 1C6H12O62 
would need to be metabolized to produce this quantity of 
CO2? (The chemical reaction is the same as that for combustion 
of C6H12O6. See Section 3.2 and Problem 10.57.)

Chemical explosions are characterized by the instantaneous release of large quantities of hot gases, which set up a shock wave of enormous pressure (up to 700,000 atm) and velocity (up to 20,000 mi/h). For example, explosion of nitroglycerin 1C3H5N3O92 releases four gases, A, B, C, and D:
n C3H5N3O91l2¡a A1g2 + b B1g2 + c C1g2 + d D1g2
Assume that the explosion of 1 mol (227 g) of nitroglycerin releases gases with a temperature of 1950 °C and a volume of 1323 L at 1.00 atm pressure.
(d) When gases C and D were passed through a hot tube of powdered copper, gas C reacted to form CuO. The remaining gas, D, was collected in a third 500.0-mL flask and found to have a mass of 0.168 g and a pressure f 223 mm Hg at 25 °C. How many moles each of C and D were present, and what are their likely identities?

Chlorine gas was first prepared in 1774 by the oxidation of 
NaCl with MnO2: 
2 NaCl1s2 + 2 H2SO41l2 + MnO21s2¡ 
Na2SO41s2 + MnSO41s2 + 2 H2O1g2 + Cl21g2 
Assume that the gas produced is saturated with water vapor 
at a partial pressure of 28.7 mm Hg and that it has a volume 
of 0.597 L at 27 °C and 755 mm Hg pressure. 
(a) What is the mole fraction of Cl2 in the gas?

Chlorine gas reacts with fluorine gas to form chlorine
trifluoride.
Cl2( g) + 3 F2( g)¡2 ClF3( g)
A 2.00-L reaction vessel, initially at 298 K, contains chlorine gas
at a partial pressure of 337 mmHg and fluorine gas at a partial
pressure of 729 mmHg. Identify the limiting reactant. Determine the theoretical yield of ClF3 in grams.

Gases: Stoichiometry

STP Gas Chemistry (Standard Temperature and Pressure) Examples Practice Problems Questions Shortcut

Ammonium carbonate decomposes upon heating according to
the balanced equation:
(NH4)2CO3(s)¡ 2 NH3( g) + CO2( g) + H2O( g)
Calculate the total volume of gas produced at 22 °C and 1.02 atm
by the complete decomposition of 11.83 g of ammonium carbonate.

The air in a bicycle tire is bubbled through water and collected
at 25 °C. If the total volume of gas collected is 5.45 L at a temperature of 25 °C and a pressure of 745 torr, how many moles of
gas were in the bicycle tire?

Consider the chemical reaction:
C(s) + H2O( g)¡CO( g) + H2( g)
How many liters of hydrogen gas are formed from the complete
reaction of 15.7 g C? Assume that the hydrogen gas is collected at
a pressure of 1.0 atm and a temperature of 355 K.

Modern pennies are composed of zinc coated with copper. A
student determines the mass of a penny to be 2.482 g and then
makes several scratches in the copper coating (to expose the underlying
zinc). The student puts the scratched penny in hydrochloric
acid, where the following reaction occurs between the
zinc and the HCl (the copper remains undissolved):
Zn(s) + 2 HCl(aq)¡ H2( g) + ZnCl2(aq)
The student collects the hydrogen produced over water at 25 °C.
The collected gas occupies a volume of 0.899 L at a total pressure
of 791 mmHg. Calculate the percent zinc (by mass) in the penny.
(Assume that all the Zn in the penny dissolves.)

Binary compounds of alkali metals and hydrogen react with
water to liberate H2( g). The H2 from the reaction of a sample of
NaH with an excess of water fills a volume of 0.490 L above the
water. The temperature of the gas is 35 °C and the total pressure
is 758 mmHg. Determine the mass of H2 liberated and the mass
of NaH that reacted.

Determine the mass (in grams) of water formed when 15.3 L NH3&nbsp;(at 298 K and 1.50 atm) is reacted with 21.7 L of O2 (at 323 K and 1.1 atm). 4 NH3 (g) + 5 O2 (g) → 4 NO (g) + 6 H2O (g)

Gaseous compound Q contains only xenon and oxygen. 
When 0.100 g of Q is placed in a 50.0-mL steel vessel at 
0 °C the pressure is 0.229 atm. 
(b) When the vessel and its contents are warmed to 100 °C, Q 
decomposes into its constituent elements. What is the 
total pressure, and what are the partial pressures of 
xenon and oxygen in the container?

Oxygen gas reacts with powdered aluminum according to the
reaction:
4 Al(s) + 3 O2( g)¡2 Al2O3(s)
What volume of O2 gas (in L), measured at 782 mmHg and 25 °C,
completely reacts with 53.2 g Al?

Assume that a single cylinder of an automobile engine has
a volume of 524 cm3. (a) If the cylinder is full of air at 74 C
and 99.3 kPa, how many moles of O2 are present? (The
mole fraction of O2 in dry air is 0.2095.) (b) How many
grams of C8H18 could be combusted by this quantity of
O2, assuming complete combustion with formation of
CO2 and H2O?

Assume that you have 1.00 g of nitroglycerin in a 500.0-mL 
steel container at 20.0 °C and 1.00 atm pressure. An explosion 
occurs, raising the temperature of the container and its 
contents to 425 °C. The balanced equation is 
4 C3H5N3O91l2¡ 
12 CO21g2 + 10 H2O1g2 + 6 N21g2 + O21g2 
(c) What is the pressure in atmospheres inside the container 
after the explosion according to the ideal gas law?

Molar Gas Volume: Stoichiometry With Gases

A 5.00-L vessel contains 25.0 g of PCl3 and 3.00 g of O2 at 15 °C. The vessel is heated to 200.0 °C, and the contents react to give POCl3. What is the final pressure in the vessel, assuming that the reaction goes to completion and that all reactants and products are in the gas phase?

A steel container with a volume of 500.0 mL is evacuated, 
and 25.0 g of CaCO3 is added. The container and contents 
are then heated to 1500 K, causing the CaCO3 to decompose 
completely, according to the equation 
CaCO31s2¡CaO1s2 + CO21g2. 
(a) Using the ideal gas law and ignoring the volume of any 
solids remaining in the container, calculate the pressure 
inside the container at 1500 K.

Gas Stoichiometry Example 1

Calcium hydride, CaH2, reacts with water to form hydrogen
gas:
CaH21s2 + 2 H2O1l2¡Ca1OH221aq2 + 2 H21g2
This reaction is sometimes used to inflate life rafts, weather
balloons, and the like, when a simple, compact means of
generating H2 is desired. How many grams of CaH2 are
needed to generate 145 L of H2 gas if the pressure of H2 is
110 kPa at 21 °C?

Titanium(III) chloride, a substance used in catalysts for preparing
polyethylene, is made by high-temperature reaction
of TiCl4 vapor with H2:
2 TiCl41g2 + H21g2¡2 TiCl31s2 + 2 HCl1g2
(a) How many grams of TiCl4 are needed for complete reaction
with 155 L of H2 at 435 °C and 795 mm Hg pressure?

A sample of magnesium metal reacts with aqueous HCl to 
yield H2 gas: 
Mg1s2 + 2 HCl1aq2¡MgCl21aq2 + H21g2 
The gas that forms is found to have a volume of 3.557 L 
at 25 °C and a pressure of 747 mm Hg. Assuming that the 
gas is saturated with water vapor at a partial pressure of 
23.8 mm Hg, what is the partial pressure in millimeters of 
mercury of the H2? How many grams of magnesium metal 
were used in the reaction?

An empty 4.00-L steel vessel is filled with 1.00 atm of CH41g2 and 4.00 atm of O21g2 at 300 °C. A spark causes the CH4 to burn completely, according to the equation
CH41g2 + 2 O21g2¡CO21g2 + 2 H2O1g2 ΔH° = -802 kJ
(a) What mass of CO21g2 is produced in the reaction?

Both Jacques Charles and Joseph Louis Guy-Lussac were avid
balloonists. In his original flight in 1783, Jacques Charles
used a balloon that contained approximately 31,150 L of H2.
He generated the H2 using the reaction between iron and hydrochloric
acid:
Fe1s2 + 2 HCl1aq2 ¡ FeCl21aq2 + H21g2
How many kilograms of iron were needed to produce this
volume of H2 if the temperature was 22 °C?

Gaseous iodine pentafluoride, IF5, can be prepared by the
reaction of solid iodine and gaseous fluorine:
I21s2 + 5 F21g2¡2 IF51g2
A 5.00-L flask containing 10.0 g of I2 is charged with
10.0 g of F2, and the reaction proceeds until one of
the reagents is completely consumed. After the reaction
is complete, the temperature in the flask is 125 °C.
(a) What is the partial pressure of IF5 in the flask?

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[BOOK CHEM] Clutch Version

Partial Pressure

Partial Pressure (PGas) is the pressure exerted by an individual gas within a container.

Velocity Distributions

Velocity Distributions represent probability distributions for a gas when examining their molar mass and temperature.

Mole Fraction

Mole Fraction (X) represents the mole component by total moles.&nbsp;

Mole Fraction -

The Ideal Gas Law Derivations

The&nbsp;Ideal Gas Law Derivations are a convenient way to solve gas calculations involving 2 sets of the same variables.&nbsp;

Root Mean Square Speed

Root Mean Square Speed&nbsp;allows for the determination of the velocity of 1 type of gas molecule.

The Ideal Gas Law: Density

Under certain conditions of pressure and temperature, the Ideal Gas Law can determine the density&nbsp;of a gas.&nbsp;

Effusion

Effusion is the escaping of gas molecules or atoms through a pinhole.&nbsp;

Kinetic Energy of Gases

Kinetic Energy is the energy an object possesses due to its motion.

Gas Stoichiometry involves chemical reactions that contain gases.

The Ideal Gas Law

The Ideal Gas Law formula relates the behavior of gases under varying conditions of pressure, volume, moles and temperature.

Chemistry Gas Laws: Combined Gas Law

The Combined Gas Law&nbsp;is created from “combining” Boyle’s Law, Charles’ Law, and Gay–Lussac’s Law.

Pressure Units

Pressure is the force that is exerted within a given volume of space.&nbsp;

Kinetic Molecular Theory

A gas is seen as a collection of molecules or individual atoms that are in constant motion. The Kinetic-Molecular Theory tries to use data of real gases to predict how an ideal gas would behave if they existed.&nbsp;&nbsp;

Standard Temperature and Pressure

In order to accurately study the effect that changes in pressure, temperature and moles have on volume, chemists will often run their experiments under Standard Temperature and Pressure.&nbsp;

The Ideal Gas Law Applications

The Ideal Gas Law Applications establish both the direct and inverse relationships between the Ideal Gas Law variables.

Maxwell-Boltzmann Distribution

The Maxwell-Boltzmann Distribution is a probability distribution curve that describes the speed of a gas at a specific temperature.

Chemistry Gas Laws

Chemistry Gas Laws&nbsp;are laws that relate together the pressure, volume and temperature of a gas.

The Ideal Gas Law: Molar Mass

The Ideal Gas Law can be further extended to find the molar mass of a gas.&nbsp;

Van der Waals Equation

The&nbsp;Van der Waals Equation is used when dealing with real, non-ideal gases.&nbsp;