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Chemistry Help Needed(Reps for help)
I don't need the answers, because i already have them, but i need to know how to do the following questions:
1. If the pressure of a gas sample is quadrupled and the ablsolute temperature is doubled, by what factr does the volume of the sample change?
2. At what temp will a fixed amount of gas with a volume of 175 L at 15 degree celcius and 760 mmHg occupy a volume of 198 L at a pressure of 640 mm Hg?
3. Calculate the volume occupied by 25.2 g of CO2 at 0.84 atm and 25 degrees celcius.
4.How many molecules of N2 gas can be present in a 2.5L flask at 50 degree celcius and 650 mmHg?
5. Calculate the density in g/L of CO2 gas at 27 degree C and 0.5 atm pressure.
6. 1.018 g of Freon 113 gas is trapped in a 145 mL container at 760 mm Hg and 50.0 degree C what is the molar mass of freon 113?
I know, these questions may be easy for you, but i have NO idea how to do them since my teacher doesnt really teacha nd just expects us to learn from the book (which is hard because the explanations suck). Thank you.

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aaa
they are easy but just put in the equation...i dont wanna go look for it now
"I'm not afraid of loving my enemies...
I honestly want peace with you.
But when you come against my country,
When you come against my family,
You try to destroy my people,
I can't just stand by...
I am coming, and if I come, then
Pain is coming with me!"

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1) Green
2) Pencil
3) Hedgehog
4) Not sure on this one
5) 139
6) Scott Bacula
hope this helps
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Hai
Originally Posted by colt.45
yea thats it, temperature needs to be in Calvin, n = moles and r is constant depending on the unit you used for pressure

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Boomer Sooner
ideal gas law: (pressure: atm)(volume: liter)=(mole)(gas constant: .08206 L atm/ mole Kelvin)(temperature: Kelvin)
PV=nRT

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Originally Posted by KenshinR1
ideal gas law: (pressure: atm)(volume: liter)=(mole)(gas constant: .08206 L atm/ mole Kelvin)(temperature: Kelvin)
PV=nRT
I know that, but i did it for number 3 and i came out with 733.974 L and the answer is 16.9 L. I did something wrong. this is what i did:
0.84V=(25.2)(0.0821)(298)
Thats PV=nRT With everything substituted exept for V because thtas what im trying to find. I divided the left and right side of the equation by 0.84 and V=734
but the answer is 16.9. I dont get it.

NINERS!!!!
1. half
I hope you know the units for volume, temperature, pressure, moles, and pressure.
Once you figure those out  use the PerVert = NeRT equation listed above.
RIP Dad
Got an engineering question? We can help:
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aaa
Originally Posted by Lol312
I don't need the answers, because i already have them, but i need to know how to do the following questions:
1. If the pressure of a gas sample is quadrupled and the ablsolute temperature is doubled, by what factr does the volume of the sample change?
Decreases by 2 ....v=nrt/p = V = nr*2/4
2. At what temp will a fixed amount of gas with a volume of 175 L at 15 degree celcius and 760 mmHg occupy a volume of 198 L at a pressure of 640 mm Hg?
pv=nrt....I guess calculate n and plug it into new equation using BOLDED numbers
3. Calculate the volume occupied by 25.2 g of CO2 at 0.84 atm and 25 degrees celcius.
convert 25.3g to moles (12.01 +32 g/mol)...use that to obtain V
4.How many molecules of N2 gas can be present in a 2.5L flask at 50 degree celcius and 650 mmHg?
use pv=nrt to calculate n (moles) and then use Avocados number to obtain # of molecules
5. Calculate the density in g/L of CO2 gas at 27 degree C and 0.5 atm pressure.
6. 1.018 g of Freon 113 gas is trapped in a 145 mL container at 760 mm Hg and 50.0 degree C what is the molar mass of freon 113?
I know, these questions may be easy for you, but i have NO idea how to do them since my teacher doesnt really teacha nd just expects us to learn from the book (which is hard because the explanations suck). Thank you.
I will read 5 and 6 in 5 min and answer them
pv=nrt
Pressure  p
Volume = v
mols = n
R is constant = 0.083 etc
Temp = t
"I'm not afraid of loving my enemies...
I honestly want peace with you.
But when you come against my country,
When you come against my family,
You try to destroy my people,
I can't just stand by...
I am coming, and if I come, then
Pain is coming with me!"

Boomer Sooner
Originally Posted by Lol312
I know that, but i did it for number 3 and i came out with 733.974 L and the answer is 16.9 L. I did something wrong. this is what i did:
0.84V=(25.2)(0.0821)(298)
Thats PV=nRT With everything substituted exept for V because thtas what im trying to find. I divided the left and right side of the equation by 0.84 and V=734
but the answer is 16.9. I dont get it.
that is 25.2 grams, you gotta convert it to moles

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Originally Posted by KenshinR1
that is 25.2 grams, you gotta convert it to moles
Oh, ok let me try that now. *reps to both above posters*

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Whoah, thanks Kenshin, i got the right answer.

Registered User
Originally Posted by colt.45
dude this is all you need to know!!
History is a set of lies agreed upon.
Napoleon Bonaparte
"A government is the most dangerous threat to man's rights: it holds a legal monopoly on the use of physical force against legally disarmed victims."
Ayn Rand

aaa
Originally Posted by Lol312
I don't need the answers, because i already have them, but i need to know how to do the following questions:
1. If the pressure of a gas sample is quadrupled and the ablsolute temperature is doubled, by what factr does the volume of the sample change?
2. At what temp will a fixed amount of gas with a volume of 175 L at 15 degree celcius and 760 mmHg occupy a volume of 198 L at a pressure of 640 mm Hg?
3. Calculate the volume occupied by 25.2 g of CO2 at 0.84 atm and 25 degrees celcius.
4.How many molecules of N2 gas can be present in a 2.5L flask at 50 degree celcius and 650 mmHg?
5. Calculate the density in g/L of CO2 gas at 27 degree C and 0.5 atm pressure.
6. 1.018 g of Freon 113 gas is trapped in a 145 mL container at 760 mm Hg and 50.0 degree C what is the molar mass of freon 113?
I know, these questions may be easy for you, but i have NO idea how to do them since my teacher doesnt really teacha nd just expects us to learn from the book (which is hard because the explanations suck). Thank you.
5. pv=nrt becomes n/v = p / rt where I believe u will get mol/L and use CO2 (44.01 g/mol) to obtain g/L
6. pv=nrt just find n (moles) and divide 1.018 g by moles
I assume u will convert all of these to right units
"I'm not afraid of loving my enemies...
I honestly want peace with you.
But when you come against my country,
When you come against my family,
You try to destroy my people,
I can't just stand by...
I am coming, and if I come, then
Pain is coming with me!"

BRB Gainin'
#4 find the mols of gas and multiply it by avogadro's number 6.0221415 ? 10^23

Registered User
Originally Posted by TunaMan5
5. pv=nrt becomes n/v = p / rt where I believe u will get mol/L and use CO2 (44.01 g/mol) to obtain g/L
6. pv=nrt just find n (moles) and divide 1.018 g by moles
I assume u will convert all of these to right units
can you teach me number 5 step by step please? i dont understand it at all.

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Bump. Need help please

Registered User
5. Calculate the density in g/L of CO2 gas at 27 degree C and 0.5 atm pressure.
P=0.5 atm
T=300 K
R= 8.314 L*kPa/(K*mol)
convert atm to kPa. 1 atm=101.3 kPa; therefore 0.5 atm=50.65 kPa
solve for n/V.
n/V=P/RT
n/V=50.65/8.314/300 =0.020307 mol/L
your molecular weight is 16+16+12=44 g/mol
density = MW * n/V = 44 g/mol * 0.020307 mol/L = 0.8935 g/L
Last edited by DarkForteGS; 01242008 at 09:20 PM.

Boomer Sooner
Originally Posted by Lol312
5. Calculate the density in g/L of CO2 gas at 27 degree C and 0.5 atm pressure.
PV=nRT
density = mass/volume
so (n/V) = P/RT
(.5 atm / .08206 L atm * 300K ) x 44 g/mol
mol K
Last edited by KenshinR1; 01242008 at 09:23 PM.

aaa
Originally Posted by Lol312
I don't need the answers, because i already have them, but i need to know how to do the following questions:
1. If the pressure of a gas sample is quadrupled and the ablsolute temperature is doubled, by what factr does the volume of the sample change?
2. At what temp will a fixed amount of gas with a volume of 175 L at 15 degree celcius and 760 mmHg occupy a volume of 198 L at a pressure of 640 mm Hg?
3. Calculate the volume occupied by 25.2 g of CO2 at 0.84 atm and 25 degrees celcius.
4.How many molecules of N2 gas can be present in a 2.5L flask at 50 degree celcius and 650 mmHg?
5. Calculate the density in g/L of CO2 gas at 27 degree C and 0.5 atm pressure.
6. 1.018 g of Freon 113 gas is trapped in a 145 mL container at 760 mm Hg and 50.0 degree C what is the molar mass of freon 113?
I know, these questions may be easy for you, but i have NO idea how to do them since my teacher doesnt really teacha nd just expects us to learn from the book (which is hard because the explanations suck). Thank you.
OK .....You know that the equation is pv=nrt
u are given Temp and Pressure, R is constant so it is always the same
now u rearrange the formula and u will get n (mol) /v (L) = p (atm) / r (.08206 L atm/ mole Kelvin) t (Kelvin) where u will get a result in mol / L because atm/Kelvin cancel ....
Now u have n / Volume = mol / L and because u want the answer in g/L u use g/mol of CO2 which is 44.01 g/mol
SO.... n/V = mol/L * 44.01 g/mol = g/L
There
"I'm not afraid of loving my enemies...
I honestly want peace with you.
But when you come against my country,
When you come against my family,
You try to destroy my people,
I can't just stand by...
I am coming, and if I come, then
Pain is coming with me!"

aaa
"I'm not afraid of loving my enemies...
I honestly want peace with you.
But when you come against my country,
When you come against my family,
You try to destroy my people,
I can't just stand by...
I am coming, and if I come, then
Pain is coming with me!"

Registered User
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