Solutions and States of Matter - AP Chemistry
Card 0 of 2320
A gas is at STP
What does STP refer to?
A gas is at STP
What does STP refer to?
Standard temperature and pressure is 00C and 1 atm
Standard temperature and pressure is 00C and 1 atm
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COCl2 (g) ⇌ CO (g) + Cl2 (g)
Initially a reaction chamber contains only 2 moles of COCl2, after the reaction has reached the equilibrium shown above the pressure is measures to be 2.60 atm. What is the most likely cause for the increase in pressure?
COCl2 (g) ⇌ CO (g) + Cl2 (g)
Initially a reaction chamber contains only 2 moles of COCl2, after the reaction has reached the equilibrium shown above the pressure is measures to be 2.60 atm. What is the most likely cause for the increase in pressure?
The equilibrium expression indicates that one mole of COCl2(g) will decompose into CO (g) and Cl2 (g). One mole of gas is present on the left side of the equation, and two moles of gas are present on the right side of the equation. The increases in pressure is due to the increase in the number of gas molecules in the reaction chamber.
The equilibrium expression indicates that one mole of COCl2(g) will decompose into CO (g) and Cl2 (g). One mole of gas is present on the left side of the equation, and two moles of gas are present on the right side of the equation. The increases in pressure is due to the increase in the number of gas molecules in the reaction chamber.
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What is the osmotic pressure exerted by a solution of 2M CaCl2 at room temperature? (R=0.082 L*atm/K/mol)
What is the osmotic pressure exerted by a solution of 2M CaCl2 at room temperature? (R=0.082 L*atm/K/mol)
The van't Hoff factor for CaCl2 is 3 since the molecule dissociates in solution to 3 ions. T is in absolute temperature (25+273=298). This makes the osmotic pressure:
3*2M*0.082*298.
The van't Hoff factor for CaCl2 is 3 since the molecule dissociates in solution to 3 ions. T is in absolute temperature (25+273=298). This makes the osmotic pressure:
3*2M*0.082*298.
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What is the molar mass of a gas with a density of 
at STP?
What is the molar mass of a gas with a density of
Since we have the density of the mystery gas, we can rearrange the ideal gas law so that the remaining factors are equal to the density of the gas.
We can redefine moles of gas as mass over molar mass.
We can now rearrange the equation to solve for density (mass per volume), which is given in the question.
Using this set up and the values for standard temperature and pressure, we can solve for the molar mass.
Since we have the density of the mystery gas, we can rearrange the ideal gas law so that the remaining factors are equal to the density of the gas.
We can redefine moles of gas as mass over molar mass.
We can now rearrange the equation to solve for density (mass per volume), which is given in the question.
Using this set up and the values for standard temperature and pressure, we can solve for the molar mass.
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It can be argued that one of the greatest innovations in automobile safety is the airbag. A typical driver's side airbag expands to a volume of between 50-60L. For this problem use 
. In older airbag models sodium azide is employed to produce nitrogen gas as shown in the following decomposition reaction:
Two more reactions are employed to remove the reactive sodium metal, shift the above reaction equilibrium to the right, and produce more nitrogen gas; however for this problem assume all gas is generated from the first reaction as shown above and that the reaction proceeds to completion.
The gauge pressure is 
. This is the pressure at which the airbag is deployed. Note: gauge pressure is defined as the additional pressure in the system relative to atmospheric pressure. In this case use STP pressure as atmospheric pressure.
(It is worth noting that this pressure is the initial pressure to fill the airbag, which would provide a rock-hard cushion; therefore in the real world the air bag immediately begins to deflate so as to provide proper cushioning; that fact is not important for solving this problem).
What is the minimum mass of 
required to inflate the airbag given the above conditions?
It can be argued that one of the greatest innovations in automobile safety is the airbag. A typical driver's side airbag expands to a volume of between 50-60L. For this problem use
Two more reactions are employed to remove the reactive sodium metal, shift the above reaction equilibrium to the right, and produce more nitrogen gas; however for this problem assume all gas is generated from the first reaction as shown above and that the reaction proceeds to completion.
The gauge pressure is
(It is worth noting that this pressure is the initial pressure to fill the airbag, which would provide a rock-hard cushion; therefore in the real world the air bag immediately begins to deflate so as to provide proper cushioning; that fact is not important for solving this problem).
What is the minimum mass of
First, identify the necessary parameters.
We must use the ideal gas equation:
and since the molar gas constant given uses Kelvin in it's definition, we must convert 
to Kelvin as follows: 
Since the pressure given is gauge pressure, we must convert to the actual pressure as follow: 
So therefore the pressure we want to use is 
Now that we have listed the given quantities we can see that in order to get the mass of 
needed, we must first find the number of moles of 
needed to fill the volume of the airbag, then use the molar ratios from the above chemical equation to convert moles of 
to moles of 
, after which we can use the molar mass of 
to calculate the grams of 
needed to inflate the airbag.
In order to calculate the number of moles of 
we can employ the Ideal gas law: to find n (the number of moles of gas; which in this case the only gas involved is 
Plug in the given quantities that have been converted into the correct units and quantities:
Solve.
Now that we know the moles of 
needed we can use stoichiometry, and the information in the following equation:
To determine the number of moles of 
required and then convert the moles of 
to the grams of 
using the molar mass of 
. The molar mass of 
can be found by using a periodic table and adding the molar masses of the constituent elements as shown below:
Molar mass of
Given that we calculated the moles of 
to fill the volume of the airbag to be: 
, and the molar ratios from the chemical equation we can set up the final steps of the calculation as shown below:
Therefore in order to inflate this driver's side airbag it would need to contain at least 68.04g of
First, identify the necessary parameters.
We must use the ideal gas equation:
Since the pressure given is gauge pressure, we must convert to the actual pressure as follow:
So therefore the pressure we want to use is
Now that we have listed the given quantities we can see that in order to get the mass of
In order to calculate the number of moles of
Plug in the given quantities that have been converted into the correct units and quantities:
Solve.
Now that we know the moles of
To determine the number of moles of
Molar mass of
Given that we calculated the moles of
Therefore in order to inflate this driver's side airbag it would need to contain at least 68.04g of
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Which of the following will not be found in the atmosphere for an extended period of time?
Which of the following will not be found in the atmosphere for an extended period of time?
Most gases exist as diatomic molecules in nature. 
, 
, and 
are all common gases found in the atmosphere and the air we breathe.
Ozone, 
, is a rare exception to the diatomic bonding principle, and is also found in significant quantities in the atmosphere.
Monatomic oxygen, 
, has only six valence electrons and is relatively unstable; this compound would not be found naturally in the atmosphere.
Most gases exist as diatomic molecules in nature.
Ozone,
Monatomic oxygen,
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A flexible box contains four moles of octane gas at STP with an excess of oxygen. If the octane is combusted according to the following reaction and the box is allowed to expand, what is the change in volume?
A flexible box contains four moles of octane gas at STP with an excess of oxygen. If the octane is combusted according to the following reaction and the box is allowed to expand, what is the change in volume?
This question does not acually deal with the ideal gas law, but only with the standard volume of a gas at STP. At standard temperature and pressure, one mole of gas has a volume of 22.5L.
We know that initially we have four moles of octane and excess oxygen. This means that octane will be the limiting reagent for the combustion reaction, since oxygen is in excess.
The total moles of reactant gas when utilizing all four moles of octane is 54, while the total moles of product gas is 68.
There is a total change in moles of:
Since we end the reaction with 14 more moles of gas than we started, the volume must increase:
The change in volume is 
.
This question does not acually deal with the ideal gas law, but only with the standard volume of a gas at STP. At standard temperature and pressure, one mole of gas has a volume of 22.5L.
We know that initially we have four moles of octane and excess oxygen. This means that octane will be the limiting reagent for the combustion reaction, since oxygen is in excess.
The total moles of reactant gas when utilizing all four moles of octane is 54, while the total moles of product gas is 68.
There is a total change in moles of:
Since we end the reaction with 14 more moles of gas than we started, the volume must increase:
The change in volume is
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At 
the vapor pressure of pure water is 
. What is the minimum amount of liquid water we need to put in a 
flask to achieve this vapor pressure. 
At
We use the ideal gases equation to know the mol of water we need in the gas phase to generate a pressure of 
in a 
flask at 
.
And the mass is:
If we have less than that amount of water the liquid will evaporate completely but there will not be enough molecules to reach the vapor pressure. More than 
of water will allow to reach the vapor pressure and there will be also a liquid leftover. Remember that the vapor pressure of a liquid at a fixed temperature is a constant.
We use the ideal gases equation to know the mol of water we need in the gas phase to generate a pressure of
And the mass is:
If we have less than that amount of water the liquid will evaporate completely but there will not be enough molecules to reach the vapor pressure. More than
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of 
are introduced in a 
flask. A vacuum is applied to the flask and its temperature raised to 
. At this temperature ammonium nitrate decomposes according to the reaction:
If the percent yield of this reaction is 
, which will be the total pressure of the flask after the reaction concludes. 
If the percent yield of this reaction is
Using the molecular mass we calculate the number of mol of 
:
At this moment we could apply the percentage yield, however let's live it for the end. Each mole of 
decomposed will generate 
of gas. Then the total pressure assuming 
yield will be:
Since only 
of the 
decomposes, the real total pressure will be:
Using the molecular mass we calculate the number of mol of
At this moment we could apply the percentage yield, however let's live it for the end. Each mole of
Since only
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Suppose that a container contains 
of a gaseous sample of unknown hydrocarbon at STP. If this sample occupies a volume of 
, what is the identity of the hydrocarbon?
Suppose that a container contains
In this question, we're given the mass and volume of an unknown hydrocarbon filling a container. We're asked to determine the identity of this compound.
To solve this problem, it's important to realize that for any ideal gas at STP (standard temperature and pressure), 
of the gas will equate to 
of that gas. For this question, we're told that there is present.
Now that we know how many moles of gas are in the container, we can use this information, together with the mass provided to us in the question stem, to determine the molecular mass of the unknown compound.
Looking at the answer choices, the only hydrocarbon that matches this molecular mass is ethane, 
.
In this question, we're given the mass and volume of an unknown hydrocarbon filling a container. We're asked to determine the identity of this compound.
To solve this problem, it's important to realize that for any ideal gas at STP (standard temperature and pressure),
Now that we know how many moles of gas are in the container, we can use this information, together with the mass provided to us in the question stem, to determine the molecular mass of the unknown compound.
Looking at the answer choices, the only hydrocarbon that matches this molecular mass is ethane,
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What would be the best solvent would you choose to dissolve C31H64?
What would be the best solvent would you choose to dissolve C31H64?
C31H64 is a non-polar substance and would dissolve best in a non-polar solvent like Toluene.
C31H64 is a non-polar substance and would dissolve best in a non-polar solvent like Toluene.
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A student investigates a series of compounds in a thin layer chromatography experiment. The student has a sample of three organic compounds labeled A, B, and C as well as an unknown compound. The student performs the experiment as shown on the left above and gets the results shown on the right. What organic compound is in the unknown sample?
A student investigates a series of compounds in a thin layer chromatography experiment. The student has a sample of three organic compounds labeled A, B, and C as well as an unknown compound. The student performs the experiment as shown on the left above and gets the results shown on the right. What organic compound is in the unknown sample?
The unknown sample gives a single spot that has migrated to the same amount as Sample C.
The unknown sample gives a single spot that has migrated to the same amount as Sample C.
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If 50g of NaCl are dissolved in 5 L of water what is the solute and what is the solvent?
If 50g of NaCl are dissolved in 5 L of water what is the solute and what is the solvent?
The solvent is what you the most off. In this case water is the solvent and sodium chloride is the solute.
The solvent is what you the most off. In this case water is the solvent and sodium chloride is the solute.
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Which of these solutions can be separated via chromatography?
Which of these solutions can be separated via chromatography?
Chromatography is the physical separation of components of a mixture. Answers b and c can be separated by chromatography due to their homogeneous nature. The soil and water example would be separated by filtration.
Chromatography is the physical separation of components of a mixture. Answers b and c can be separated by chromatography due to their homogeneous nature. The soil and water example would be separated by filtration.
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Which of the following would most likely form a homogeneous solution?
Which of the following would most likely form a homogeneous solution?
Like dissolves like. The NH4Cl and water mixture involves an ionic solid and a polar solvent. Examples a and b involve mixing polar/non-polar solvents and ionic and non-polar solvents.
Like dissolves like. The NH4Cl and water mixture involves an ionic solid and a polar solvent. Examples a and b involve mixing polar/non-polar solvents and ionic and non-polar solvents.
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In reality, the volume of a gas is slightly larger than the ideal volume. This is because .
In reality, the volume of a gas is slightly larger than the ideal volume. This is because .
One of the key charactersitics of an ideal gas is that gas molecules have no volume. This is obviously not the case, and the volume of the molecules must be added to the ideal volume. As a result, the real volume is slightly larger than the ideal volume.
One of the key charactersitics of an ideal gas is that gas molecules have no volume. This is obviously not the case, and the volume of the molecules must be added to the ideal volume. As a result, the real volume is slightly larger than the ideal volume.
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In reality, the pressure of a gas is slightly less than the pressure predicted for an ideal gas. This is because .
In reality, the pressure of a gas is slightly less than the pressure predicted for an ideal gas. This is because .
Ideal gas pressure only takes the repulsive forces between gas molecules into consideration. The truth is, gas molecules can also exhibit attractive forces with one another (London dispersion forces). This attractive force pulls the molecules inward and slows their velocity before striking the wall of the container. As a result, real gases exert slightly less pressure compared to the ideal pressure.
Ideal gas pressure only takes the repulsive forces between gas molecules into consideration. The truth is, gas molecules can also exhibit attractive forces with one another (London dispersion forces). This attractive force pulls the molecules inward and slows their velocity before striking the wall of the container. As a result, real gases exert slightly less pressure compared to the ideal pressure.
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A gas is behaving ideally
2 mols of the gas would have what volume at STP?
A gas is behaving ideally
2 mols of the gas would have what volume at STP?
use PV = nRT
V = nRT / P ; must covert T into K
V = (2)(0.0821)(273)/ 1
= 44.8 L
use PV = nRT
V = nRT / P ; must covert T into K
V = (2)(0.0821)(273)/ 1
= 44.8 L
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If you create a perfect vacuum and place a glass of water into the vacuum at room temperature, what will happen to the water?
If you create a perfect vacuum and place a glass of water into the vacuum at room temperature, what will happen to the water?
Boiling occurs when the vapor pressure exceeds the air pressure. There is no air pressure in a vacuum, so water at any temperature will boil in a vacuum.
Boiling occurs when the vapor pressure exceeds the air pressure. There is no air pressure in a vacuum, so water at any temperature will boil in a vacuum.
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Which of the following situations would most likely cause gases to deviate from ideal behavior?
Which of the following situations would most likely cause gases to deviate from ideal behavior?
At high pressure and low temperature two things are happening that will cause gases to deviate from ideal behavior. At low temperature the individual gas molecules are moving slower. As the pressure is increased the individual molecules are being pushed closer to one another. Thus, when the gas molecules are closer together and moving at reduced speeds they are more likely to interact with one another. Ideal gas behavior is dependent upon an absence of intermolecular interaction between the gas molecules. Therefore, the increased likelihood of intermolecular interactions between the gas molecules at increased pressure and decreased temperature is likely to cause gases to deviate from ideal behavior.
At high pressure and low temperature two things are happening that will cause gases to deviate from ideal behavior. At low temperature the individual gas molecules are moving slower. As the pressure is increased the individual molecules are being pushed closer to one another. Thus, when the gas molecules are closer together and moving at reduced speeds they are more likely to interact with one another. Ideal gas behavior is dependent upon an absence of intermolecular interaction between the gas molecules. Therefore, the increased likelihood of intermolecular interactions between the gas molecules at increased pressure and decreased temperature is likely to cause gases to deviate from ideal behavior.
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