Chemistry Class?
okay so I'm just starting chemistry and i barely know what the hell everything means so could you give me a site to quiz me on things cause I'm only learning pv=nRT and **** and i don't know what that means because i fool around in class a lot so could you help me please and thank you =D
Answer:
Ok, I will explain in my own words because I can't find the site name.
"P" is the pressure which can be in atm, mmHg, or kPa.
"V" is volume; ALWAYS in liters. convert to liters first.
"n" is the number of MOLES ONLY. If they give you something
in grams, convert that to moles.
"R" is the trickiest which is the ideal gas constant. If you start with the pressure atm, then you use the standard conditions for atm which is 1 atm. You use PV/T which is equivilant to the
"R" value. If you have 1 atm, the P in PV/T will be 1 and volume will be 22.4 and T will be 273. 22.4 and 273 won't change, they will always be the same in this equation. all you are changing is the pressure. Ex: If they give you a pressure in kPa, then the standard pressure for kPa is 101.31kPa. You just put that value into P in PV/T. so... 101.31 x 22.4/273
you multiply and then divide, that is how the constant "R" is found. T is temperature, ALWAYS in Kelvin, if they give you somthing different, first convert to Kelvins.
Below is information from a website, I posted it here because
it won't give me an html. Hope this helped. You can do it :)
Background:
Ideal Gas Law:
Pressure x Volume = Moles x Ideal Gas Constant x Temperature
Substituting in variables, the formula is:
PV=nRT
Explanation and Discussion:
The Ideal Gas Law may be the largest and most complex of the gas laws. This is in part because of the number of variables in the equation, and in part to the abstraction of an "ideal" gas that the law is built on. The Ideal Gas Law is also designed as a sort of umbrella for Boyle's, Charles', and Avogadro's laws.
First, we'll go over the parts of the equation, PV=nRT. P is pressure. Pressure can be in either atmospheres (atm) or kilopascals (kPa). V is volume in liters (L). n is the number of moles of the gas. Because moles of a substance are determined by mass divided by molecular mass, it can create an interesting variant we will discuss later. R is the Ideal Gas Constant. Depending on whether atmosphers or kilospascals were used, the value is either 0.0821 L-atm/mol-K or 8.31 L-kPa/mol-K, respectively. Temperature is in absolute degrees Kelvin.
An interesting aspect of the Ideal Gas Law is its flexibility. It contains elements that allow you to solve for other quantities, such as density or molecular mass. To solve for molecular mass:
PV=nRT - start with the equation
PV=mass/mol. mass x RT - change moles to mass(m) in grams divided by molecular mass in grams
mol. mass x PV = mRT - multiply by molecular mass
molecular mass = mRT/PV - divide by pressure and volume.
We can also see density in that last equation, m/V (grams/liter). The same equation, but with density(d) in place of mass per volume (m/V), is:
molecular mass = dRT/P
To solve just for density, the equation would become:
density = (molecular mass x pressure)/(constant x temperature)
So far, we have been skirting the concept of an ideal gas. What exactly is an ideal gas? An ideal gas is one that exactly conforms to the kinetic theory. The kinetic theory, as stated by Rudolf Clausius in 1857, has five key points. These are:
1. Gases are made of molecules in constant, random movement. Gases like Argon have 1-atom molecules.
2. The large portion of the volume of a gas is empty space. The volume of all gas molecules, in comparison, is negligible.
3. The molecules show no forces of attraction or repulsion.
4. No energy is lost in collision of molecules; the impacts are completely elastic.
5. The temperature of a gas is the average kinetic energy of all of the molecules.
Non-Ideal Behavior
The Kinetic Theory makes several assumptions about an ideal gas. These cause problems because real gases are not ideal. The main causes of error are related to pressure and temperature.
Pressure
At high pressures, the behavior of real gases changes dramatically from that predicted by the Ideal Gas Law. Under 10 atmospheres of pressure or less, Ideal Gas Law predictions are very close to real amounts and do not generate serious error.
Temperature
When the temperature of a gas is close to its liquefaction point, the behavior is very different from Ideal Gas Law predictions. With increasing temperatures, the Ideal Gas Law predictions become close to real values.
Why?
The answer is simple: ideal gases have molecular volume and show no attraction between molecules at any distance; real gas molecules have volume and show attraction at short distances. Let us first consider what pressure does. Pressure at high degrees will bring the molecules very close together. This causes more collisions and also allows the weak attractive forces to come into play. With low temperatures, the molecules do not have enough energy to continue on their path to avoid that attraction.
You might want to try paying attention in class (just the harsh reality of it). My guess is that you're now really lost and only fooling around more, so you need to do something to get caught up. You're going to have to try learning some of the material on your own, through your textbook or by asking someone else in the class who seems to know what's going on.
You might also try asking the teacher, apologizing for goofing off. I don't know how into the ideal gas law you're going, but here are websites listing the various forms of the equations and the basics. Many of the links have practice problems and answers.
http://en.wikipedia.org/wiki/ideal_gas_l...
http://dbhs.wvusd.k12.ca.us/webdocs/gasl...
http://misterguch.brinkster.net/pra009.p...
http://www.brynmawr.edu/acads/chem/chem1...
oh, my angry lottle girl
u can see:http://www.chem.wisc.edu/areas/clc/...
I would recommend www.chemskillbuilder.com. I think it costs to use the site but it is probably the best online chemistry resource that I can think of. It covers everything in your general chemistry course. The site is broken down into topics and there is a tutorial on each topic followed by a series of questions.
The website kif_ewing reccommended (chemskillbuilder.com) is a good one.
Also, some textbooks come with study guides/CDs. If not just read your textbook and see if you can get tutoring. Also, flashcards are great for memorizing things like chemical formulas and stuff.
You will do better if you pay attention in class, but I know that is easier said than done. I have an hour chemistry review every Tues./Thurs. and then a 3 and 1/2 hour lecture right after, so I am in class from 8:00 a.m. to 12:30. Sometimes it's hard to stay awake!
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Answer:
Ok, I will explain in my own words because I can't find the site name.
"P" is the pressure which can be in atm, mmHg, or kPa.
"V" is volume; ALWAYS in liters. convert to liters first.
"n" is the number of MOLES ONLY. If they give you something
in grams, convert that to moles.
"R" is the trickiest which is the ideal gas constant. If you start with the pressure atm, then you use the standard conditions for atm which is 1 atm. You use PV/T which is equivilant to the
"R" value. If you have 1 atm, the P in PV/T will be 1 and volume will be 22.4 and T will be 273. 22.4 and 273 won't change, they will always be the same in this equation. all you are changing is the pressure. Ex: If they give you a pressure in kPa, then the standard pressure for kPa is 101.31kPa. You just put that value into P in PV/T. so... 101.31 x 22.4/273
you multiply and then divide, that is how the constant "R" is found. T is temperature, ALWAYS in Kelvin, if they give you somthing different, first convert to Kelvins.
Below is information from a website, I posted it here because
it won't give me an html. Hope this helped. You can do it :)
Background:
Ideal Gas Law:
Pressure x Volume = Moles x Ideal Gas Constant x Temperature
Substituting in variables, the formula is:
PV=nRT
Explanation and Discussion:
The Ideal Gas Law may be the largest and most complex of the gas laws. This is in part because of the number of variables in the equation, and in part to the abstraction of an "ideal" gas that the law is built on. The Ideal Gas Law is also designed as a sort of umbrella for Boyle's, Charles', and Avogadro's laws.
First, we'll go over the parts of the equation, PV=nRT. P is pressure. Pressure can be in either atmospheres (atm) or kilopascals (kPa). V is volume in liters (L). n is the number of moles of the gas. Because moles of a substance are determined by mass divided by molecular mass, it can create an interesting variant we will discuss later. R is the Ideal Gas Constant. Depending on whether atmosphers or kilospascals were used, the value is either 0.0821 L-atm/mol-K or 8.31 L-kPa/mol-K, respectively. Temperature is in absolute degrees Kelvin.
An interesting aspect of the Ideal Gas Law is its flexibility. It contains elements that allow you to solve for other quantities, such as density or molecular mass. To solve for molecular mass:
PV=nRT - start with the equation
PV=mass/mol. mass x RT - change moles to mass(m) in grams divided by molecular mass in grams
mol. mass x PV = mRT - multiply by molecular mass
molecular mass = mRT/PV - divide by pressure and volume.
We can also see density in that last equation, m/V (grams/liter). The same equation, but with density(d) in place of mass per volume (m/V), is:
molecular mass = dRT/P
To solve just for density, the equation would become:
density = (molecular mass x pressure)/(constant x temperature)
So far, we have been skirting the concept of an ideal gas. What exactly is an ideal gas? An ideal gas is one that exactly conforms to the kinetic theory. The kinetic theory, as stated by Rudolf Clausius in 1857, has five key points. These are:
1. Gases are made of molecules in constant, random movement. Gases like Argon have 1-atom molecules.
2. The large portion of the volume of a gas is empty space. The volume of all gas molecules, in comparison, is negligible.
3. The molecules show no forces of attraction or repulsion.
4. No energy is lost in collision of molecules; the impacts are completely elastic.
5. The temperature of a gas is the average kinetic energy of all of the molecules.
Non-Ideal Behavior
The Kinetic Theory makes several assumptions about an ideal gas. These cause problems because real gases are not ideal. The main causes of error are related to pressure and temperature.
Pressure
At high pressures, the behavior of real gases changes dramatically from that predicted by the Ideal Gas Law. Under 10 atmospheres of pressure or less, Ideal Gas Law predictions are very close to real amounts and do not generate serious error.
Temperature
When the temperature of a gas is close to its liquefaction point, the behavior is very different from Ideal Gas Law predictions. With increasing temperatures, the Ideal Gas Law predictions become close to real values.
Why?
The answer is simple: ideal gases have molecular volume and show no attraction between molecules at any distance; real gas molecules have volume and show attraction at short distances. Let us first consider what pressure does. Pressure at high degrees will bring the molecules very close together. This causes more collisions and also allows the weak attractive forces to come into play. With low temperatures, the molecules do not have enough energy to continue on their path to avoid that attraction.
You might want to try paying attention in class (just the harsh reality of it). My guess is that you're now really lost and only fooling around more, so you need to do something to get caught up. You're going to have to try learning some of the material on your own, through your textbook or by asking someone else in the class who seems to know what's going on.
You might also try asking the teacher, apologizing for goofing off. I don't know how into the ideal gas law you're going, but here are websites listing the various forms of the equations and the basics. Many of the links have practice problems and answers.
http://en.wikipedia.org/wiki/ideal_gas_l...
http://dbhs.wvusd.k12.ca.us/webdocs/gasl...
http://misterguch.brinkster.net/pra009.p...
http://www.brynmawr.edu/acads/chem/chem1...
oh, my angry lottle girl
u can see:http://www.chem.wisc.edu/areas/clc/...
I would recommend www.chemskillbuilder.com. I think it costs to use the site but it is probably the best online chemistry resource that I can think of. It covers everything in your general chemistry course. The site is broken down into topics and there is a tutorial on each topic followed by a series of questions.
The website kif_ewing reccommended (chemskillbuilder.com) is a good one.
Also, some textbooks come with study guides/CDs. If not just read your textbook and see if you can get tutoring. Also, flashcards are great for memorizing things like chemical formulas and stuff.
You will do better if you pay attention in class, but I know that is easier said than done. I have an hour chemistry review every Tues./Thurs. and then a 3 and 1/2 hour lecture right after, so I am in class from 8:00 a.m. to 12:30. Sometimes it's hard to stay awake!
The answers post by the user, for information only, FunQA.com does not guarantee the right.
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