,Graham’s law

,Graham’s law addresses effusion or the quick and random motion of tiny gas molecules. The escape of tiny gas molecules through very small openings is defined as effusion.
Why does a helium balloon lose its helium? The helium is enclosed in a container, usually a good balloon. The holes through which the helium is escaping might be only about the size of the atoms or molecules that are escaping, so the helium can very gradually effuse through those tiny openings.
In another example, you may have a bottle of a gas sealed in a way that you think is very tight. You find that the gas has effused. Effusion is the escape of gas molecules through very small openings. The rate of this motion, how rapidly it will effuse, is definitely related to the kinetic energy of the molecules. Ek=1/2Mv¬2
V2= the mean square speed or the average square speed
M= the mass
E= kinetic energy
You should know that the kinetic energy of a gas is directly related to temperature. If you increase the temperature then you increase the kinetic energy of the gas. You are going to increase the rate at which it will effuse or escape. The law is frequently stated as: rates of effusion of different gases at the same conditions are inversely proportional to the square roots of their molecular masses. In other words, the heavier the gas, the more slowly it effuses. The lighter the gas, the faster it effuses: Ra x √(Ma=rb x √Mb) . The mass referred to is the molecular mass. Rate is always expressed per unit time. For example, it could be expressed in liters per minute.
If oxygen effuses from a container at the rate of 3.64 ml/sec, what is the molecular weight of a gas effusing from the same container at 4.48 ml/ sec? The second gas is effusing more rapidly; therefore, the second gas has a lesser molecular weight.
Ra x √(Ma=rb x √Mb)
3.64 ml/sec. X √(32g/1=) 4.48 ml/s* √Mb
√Mb=4.50
Mb= 4.50 * 4.50
Mb= 22.2 g/ mol
The second gas is significantly lighter than oxygen.

Hydrogen is less dense than air: two grams per mole. The hydrogen is moving at a greater velocity than air because smaller particles move at a greater rate of speed. As hydrogen moves through a person’s vocal cords, it will cause the vocal cords to vibrate faster and increase the pitch of the voice. Hydrogen increases the pitch of the voice because gas moves to the vocal cords at a higher rate of speed than air. A gas denser than air will move more slowly through the vocal cords, causing them to vibrate more slowly, decreasing their frequency and thus the pitch of the voice.

Graham’s Law of Diffusion


Bibliography of resources for background research

A Scottish physical chemist formulated Graham's law, better known as Graham's law of effusion. Thomas Graham discovered that the rate of effusion of a gas is inversely proportional to the square root of the mass of its particles, so it was named after him (Graham).As I stated above, he found out through experimentation that the rate of effusion of a gas is inversely proportional to the square root of the mass of its particles. I did not have to learn any new science because I understood everything that I read, for I learned about the different parts of the topic separately years ago. This does not mean that I did no research.

Notes
Gases have no definite volume.
They spread out and dwell in all the space accessible to them. This dispersal of gases is called diffusion. A gas will diffuse even if another gas is present in the same space. The molecules of gases are far enough apart to allow other gas molecules to fit in between.
Gases diffuse at different rates.
Graham's law states that, under equal conditions of temperature and pressure, gases diffuse at rates inversely proportional to the square roots of their molecular masses.
The term rate implies that something happens in a given period of time. The rate of diffusion of a gas is the distance its molecules travel per unit time.

Resources:
a. http://en.wikipedia.org/wiki/Graham's_law
b. http://www.citycollegiate.com/grahams_lawXI.htm
c. http://www.chem.tamu.edu/class/majors/tutorialnotefiles/graham.htm
d. http://www.molecularsoft.com/help/Gas_Laws-Effusion_Diffusion.htm
e. http://library.thinkquest.org/12596/graham.html


In taking the experimental error into consideration, Graham’s law work as it was supposed to. This experiment be used to find the molecular mass of an unknown gas by pulging in the numbers given and useing algebra for figuring out the rese.



“Faster-moving molecules can escape faster than others through small holes in containers, and this escape is called effusion. They can also mix more rapidly with other gases by diffusion. These are usually done under constant temperature, “and so the relative rates of diffusion or effusion of two gases A and B depend only on the molar masses MA and MB:”


In the same period of time, the distance diffused by heavier gas, which has a greater molecular mass, will be less than that of a lighter gas. In this experiment, HCl and NH3, ammonia, (two gases) willl start to diffuse at the same time from opposite ends of a glass tube. Where the two gases meet, a chemical reaction will take place producing a white powder. By comparing the ratio of the distances traveled with the ratio of the square roots of the known molecular masses of the two gases, Graham's law can be confirmed.

EQUIPMENT
Glass tube
Two dropper pipets
Safety goggles
Cotton
Lab apron
Marking pencil

MATERIALS
HCl (con.)
NH3 (ammonia)
Water (for washing the test tube)
Fan (for drying the test tube)


SAFETY
Hold concentrated HCl and the concentrated NH3 carefully avoid getting then on your skin.

PROCEDURE
1. Find glass tubing, and make sure it is completely dry. Lay the tubing on your worktable preferably with a support.
2. Place cotton in each end of the tubing.
3. Remove the cotton pieces from the tubing. Using dropper pipettes, place about five drops of concentrated HCl on the one cotton peace and five drops of concentrated NH3 on the other cotton peace.
4. Right away and at the same time, place the cotton pieces into opposite ends of the tube.
5. After some time, a white ring will form where the gases meet to form a compound, NH4C1 (ammonium chloride). Mark the place on the tube where the white ring appeared.
6. Measure the distance traveled by each gas.
7. Remove the cotton peaces and rinse the tubing with water. Then wait for it to dry. Using a fan could help make the process go faster.
9. The procedure can be repeated to be sure of the results.


OBSERVATIONS AND DATA
Trial 1, trial 2, and the average of 2 trials
Distance traveled by NH3 35, 34.5, and 34.75
Distance traveled by HCl 16, 16.5, and 16.25
Molecular masses are: NH3 = 17
HCl = 36,5

CALCULATIONS:
1. Calculate the ratio: Distance NH3/ Distance HCl

Trial 1 35/16
2. Calculate the ratio: Distance NH3/ Distance HCl

Trial 2 34.5/16.5