Henry's Law and Gas Solubility Explained
Summary
TLDRThis script explores Henry's Law, demonstrating how gas solubility in a liquid is affected by pressure. Using carbon dioxide in water, it shows that doubling the pressure quadruples solubility. The script applies Henry's Law to predict how much CO2 escapes from an opened soda bottle, illustrating a practical application of the law in everyday life.
Takeaways
- đ§Ș The pressure of a gas above a liquid affects its solubility in that liquid.
- đŠ Experiments with equal-sized vessels demonstrate how pressure impacts gas solubility.
- đ Henry's Law states that the solubility of a gas in a liquid is directly proportional to the partial pressure of the gas.
- đ As pressure increases, the solubility of a gas in a liquid doubles with each doubling of pressure.
- đż The example of carbon dioxide dissolving in water is used to illustrate Henry's Law.
- đ„€ Soda bottles are pressurized with carbon dioxide to keep the bubbles dissolved until opened.
- đš When a soda bottle is opened, the pressure of CO2 drops, leading to the release of gas and the soda going flat.
- đ Henry's Law constant for CO2 is used to calculate the expected amount of gas that will escape from an opened soda.
- đ A calculation shows that approximately 2.7 liters of CO2 will escape from a 1-liter soda over a few hours.
- đŹ A modern trick allows observing the gas release effect without waiting for the soda to go flat naturally.
Q & A
What is the relationship between the pressure of a gas above a liquid and its solubility?
-The solubility of a gas in a liquid is directly proportional to the pressure of the gas above the liquid, as described by Henry's Law.
What is Henry's Law?
-Henry's Law states that the solubility of a gas in a liquid is equal to the product of Henry's constant for that gas and the partial pressure of the gas above the liquid.
How does the experiment with three vessels of water and varying amounts of CO2 demonstrate Henry's Law?
-The experiment shows that doubling the pressure of CO2 above the water doubles the solubility of CO2 in the water, illustrating a linear relationship between pressure and solubility.
What is the role of Henry's constant in Henry's Law?
-Henry's constant is a proportionality constant that relates the solubility of a specific gas to its partial pressure in a solution at a given temperature.
Why does the amount of gas dissolved in soda decrease when the bottle is opened?
-When a soda bottle is opened, the pressure of CO2 decreases significantly, leading to a decrease in solubility according to Henry's Law, causing the gas to effervesce.
What is the typical pressure of CO2 in a closed soda bottle?
-The typical pressure of CO2 in a closed soda bottle is about 4.0 atmospheres.
How is the solubility of CO2 in water calculated using Henry's Law?
-The solubility of CO2 in water is calculated by multiplying Henry's constant for CO2 (3.1 x 10^-2 mole per liter atmosphere) by the partial pressure of CO2 (4 atmospheres in a closed bottle).
What happens to the solubility of CO2 in soda when the bottle is opened?
-When the soda bottle is opened, the partial pressure of CO2 drops to nearly zero, resulting in a significant decrease in CO2 solubility.
How much CO2 is expected to escape from a soda bottle once it's been opened?
-About 2.7 liters of CO2 is expected to escape from a 1-liter soda bottle once it's been opened, based on the calculation using Henry's Law.
What is the significance of the Henry's Law constant being a constant?
-The Henry's Law constant being a constant allows for the prediction of gas solubility changes with pressure changes, as it does not vary with pressure.
What is the practical application of understanding the relationship between gas pressure and solubility in beverages like soda?
-Understanding this relationship is crucial for maintaining the fizz in carbonated beverages and for the design of processes that involve gas dissolution, such as in soft drink production.
Outlines
đ§Ș Henry's Law and Gas Solubility
This paragraph discusses the relationship between the pressure of a gas above a liquid and the solubility of that gas in the liquid. The presenter uses three equal-sized vessels with water, leaving headspace to introduce carbon dioxide (CO2) at varying pressures. It is explained that doubling the pressure of CO2 also doubles its solubility in water, following Henry's Law. The law states that the solubility of a gas is equal to Henry's constant multiplied by the partial pressure of the gas. The presenter then applies Henry's Law to predict the amount of CO2 that escapes from a soda bottle when opened, showing how the solubility of CO2 decreases dramatically when the pressure drops from 4 atmospheres to near zero.
đ Chemistry in Our Universe
The second paragraph introduces the presenter's new project, a 60-lecture course in general chemistry named 'Chemistry in Our Universe'. The course is produced in collaboration with 'Two Great Courses'. The presenter invites viewers to learn more about the project by visiting the website and searching for the course. The presenter also directs viewers to their YouTube channel for more content, and the paragraph ends with musical and applause elements, suggesting a lively and engaging presentation style.
Mindmap
Keywords
đĄPressure
đĄSolubility
đĄHenry's Law
đĄHeadspace
đĄCarbon Dioxide
đĄIdeal Gas Law
đĄPartial Pressure
đĄHenry's Constant
đĄEffervescence
đĄMoles
đĄAtmosphere
Highlights
The pressure of a gas above a liquid can affect its solubility in that liquid.
Using three equal-sized vessels to demonstrate the effect of gas pressure on solubility.
Leaving headspace in the vessels to add gas samples.
Carbon dioxide is used as the gas sample to test solubility.
Doubling the amount of CO2 in each subsequent vessel to double the pressure.
As pressure doubles, solubility also doubles, following a linear mathematical relationship.
Introducing Henry's Law, which states that gas solubility is equal to Henry's constant times the partial pressure of the gas.
Henry's Law allows predicting gas solubility as it is pressurized or depressurized.
Using Henry's Law to solve a problem involving a soda bottle pressurized with carbon dioxide.
The headspace inside a soda bottle typically has about 4.0 atmospheres of pure carbon dioxide.
Upon opening a soda bottle, carbon dioxide escapes due to the drop in pressure.
Calculating the solubility of CO2 using Henry's Law constant and the partial pressure in a closed bottle.
The Henry's Law constant for carbon dioxide is 3.1 times 10 to the minus 2 mole per liter atmosphere.
The solubility of CO2 in water under 4 atmospheres of pressure is calculated to be 1.2 times 10 to the minus 1 moles per liter.
After opening the bottle, the solubility of CO2 drops significantly due to the pressure decrease.
The new solubility of CO2 in soda after opening is only 1.2 times 10 to the minus 5 moles per liter.
Assuming all the initially soluble CO2 will escape, about 2.7 liters of carbon dioxide will be released from a 1-liter soda.
A trick to observe the CO2 release effect without waiting is mentioned, to be explored later.
The clip is from a project called 'Chemistry in Our Universe', a 60-lecture course in general chemistry.
The project is produced in collaboration with 'The Great Courses'.
Transcripts
let's take a little bit of time and
think about how the pressure of a gas
above a liquid can affect its solubility
in that liquid to do this I'm going to
use three vessels equal in size I'm
going to add to them equal volumes of
water as well but this time I'm not
going to fill them all the way to the
top I'm going to leave some headspace
available here now let's imagine that in
that headspace I can place a sample of
gas and I can make that gas as high or
low pressure as I choose in this case
we'll do carbon dioxide in
my leftmost vessel I'm going to put a
small amount of co2 so whatever pressure
this may correspond to let's double that
in the second vessel so twice as many
moles of gas in the same volume the same
temperature should give me double the
pressure for our ideal gas law
let's do it one more time we'll double
the pressure yet again in our third
vessel by adding another equivalent of
our co2 now if we were to look at the
solutions beneath these head spaces that
are filled with gas at various pressures
we would find different amounts of that
gas dissolved inside of that solution in
fact what we would find is that as we
double the pressure each time we also
double the solubility notice that here
I've gone from two to four to ultimately
eight depending upon how much of this
stuff I've done so each time I double
the pressure I double the solubility
that is a linear mathematical
relationship and it's a very simple
equation that leads to a very powerful
law Henry's law the equation is the
solubility of a gas is
equal to a constant called Henry's
constant times the partial pressure of
that gas now since I've been using pure
gases in my example here the partial
pressure of the gas would be the total
pressure of that gas within the system
and nothing else but Henry's law is
really quite interesting in hell it
allows us to predict the solubility of a
gas and how it will vary as we
pressurize and depressurize that gas
above the solution so let's put Henry's
law to use and solve a problem
soda bottled under an atmosphere of
carbon dioxide gas in order to keep the
bubbles dissolved into the soda before
you open it now typically that headspace
inside of your soda has a pressure of
about 4.0 atmospheres of pure carbon
dioxide so when you open the bottle you
hear that rush of gas escaping that's
the four atmosphere of carbon dioxide
escaping the bottle now ordinary
atmospheric gases rush back in but the
partial pressure of carbon dioxide drops
to practically nothing so the question
we're going to ask here is this how much
gas can we expect to effervesce from a
soda once it's been opened total of all
the gas were to escape at once how much
would we get well let's figure that out
to answer the question we're going to
use Henry's law and in order to use
Henry's law we have to go to a table and
find the Henry's law constant for carbon
dioxide now we can calculate the
solubility of co2 under that atmost at
four atmosphere pressure of carbon
dioxide
we're going to have to use a Henry's law
constant of 3.1 times 10 to the minus 2
mole per liter atmosphere and we're
going to multiply that by the partial
pressure of co2 in this case 4
atmospheres in a closed bottle a quick
unit analysis lets me know that I've got
the equation right I'm going to get an
answer of moles per liter and
in this case it comes out to 1.2 times
10 to the minus 1 moles per liter that's
the total amount of carbon dioxide
that's soluble in water under an
atmosphere of 4 atmosphere carbon
dioxide
but once that bottle is open something
changes namely the pressure notice that
the Henry's law constant does not change
that's why it's a constant but the
pressure has dropped all the way down to
practically nothing about 4 times 10 to
the minus 4 atmospheres a factor of
10,000 difference meaning that the new
solubility of co2 in your soda is only
1.2 times 10 to the minus 5 moles per
liter now that's so low that it's
negligible so let's finish our problem
by assuming that all of the 1.2 times 10
to the minus 1 molar co2 will be
escaping
well 1.2 times 10 to the minus minus one
moles coming from a 1 liter solution at
standard temperature and pressure we
know should occupy 20 2.4 liters so when
we do the math here we get our leaders
for our units we discover that about 2.7
liters of carbon dioxide will escape
slowly and lazily from your soda as it
goes flat over the period of a few hours
now there's a really great trick that's
become popular in recent years it allows
you to observe that effect without
having to wait we'll check that one out
in just a minute the preceding is a clip
from my new project entitled chemistry
in our universe how it all works a 60
lecture course in general chemistry
produced in collaboration with two great
courses to learn more about this project
go to WWE our courses comm and search
chemistry and our universe to learn more
about me check out my youtube channel at
youtube.com slash chem survival
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you
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