I posted this question on April 16 and received lots of help..but need more.. thanks
Use the following information to identify element A and come
pound B, then answer questions a and b.
An empty glass container has a mass of 658.572 g. It has a
mass of 659.452 g after it has been filled with nitrogen gas at a
pressure of 790. torr and a temperature of 15°C. When the container
is evacuated and refilled with a certain element (A) at a
pressure of 745 torr and a temperature of 26"C, it has a mass of
660.59 g.
Compound B, a gaseous organic compound that consists of
85.6% carbon and 14.4% hydrogen by mass, is placed in a stainless
steel vessel (10.68 L) with excess oxygen gas. The vessel is
placed in a constant-temperature bath at 22°C. The pressure in
the vessel is 1 1.98 atm. In the bottom of the vessel is a container
that is packed with Ascarite and a desiccant. Ascarite is asbestos
impregnated with sodium hydroxide; it quantitatively absorbs
carbon dioxide:
2NaOH(s) + CO2(g) -----> Na2CO3(s) H2O(l)
The desiccant is anhydrous magnesium perchlorate, which
quantitatively absorbs the water produced by the combustion reaction
as well as the water produced by the above reaction. Neither
the Ascarite nor the desiccant reacts with compound B or
oxygen. The total mass of the container with the Ascarite and
desiccant is 765.3 g.
The combustion reaction of compound B is initiated by a
spark. The pressure immediately rises, then begins to decrease,
and finally reaches a steady value of 6.02 atm. The stainless steel
vessel is carefdly opened, and the mass of the container inside
the vessel is found to be 846.7 g.
A and B react quantitatively in a 1: 1 mole ratio to form one
mole of the single product, gas C.
a. How many grams of C will be produced if 10.0 L of A and
8.60 L of B (each at STP) are reacted by opening a stopcock
connecting the two samples?
b. What will be the total pressure in the system?
I already have A: Cl2
I know that the molecular formula for B is C2H4
How do I find gas C?
for question a. I was thinking of using n=pv/rt to get the moles of A and B at stp with the respective volumes (10.0L and 8.60L). But that wouldn't make sense because once they are joined, they are no longer at STP right? But to do anything I first need to know what gas C is right?
Do you know what C2H4 is?
If you know the identity of C2H4, then it will be apparent what C is when A and B are mixed.
it's ethylene.. so is that C? I'm confused.
Isn't C2H4 the molecular formula of B?
You are right. C2H4 is compound B and compound B is ethylene. I am sure you know that ethylene has a double bond.
H2C=CH2
Now, the problem states that
A + B ==> C and we know that double bonds simply add Cl2 across the double bond; therefore,
Cl2 + C2H4 ==>ClH2C-CH2Cl
ClH2C-CH2Cl is compound C.
so to find C it was just a matter of adding the two compounds together and nothing else?
okay so now that I have C was I right about using n=pv/rt to find moles of A and B?
You may do that to find mols A and B and react them to determine mols of C and it is obvious from the equation that 1 mol A reacts with 1 mol B to form 1 mol C so its all 1:1:1. There is a short cut you can use; i.e., when reactants and products are gases, you need not convert to mols first. You can simply use liters to react with liters to produce liters. But you use the process with which you feel comfortable. C2H4, by the way, is the limiting reagent.
yes, I don't know how to go from liters to liters.. so
moles a:
n=(1)(10)/(0.082057)(273) = 0.446 mols Cl2
moles b:
(1)(8.60k) /(0.082057)(273) = 0.384mols C2H4
Grams C gas produced:
from Cl2:
(0.446mols Cl2)(1/1)(98.952gCgas/1molCgas) = 44.133g Cgas
from C2H4:
0.384molsB * 98.952= 37.998g Cgas
C2H4 is indeed the limiting reagent and 37.998 g Cgas will be formed.
To find the answer for b:total pressure in the system I was thinking of adding the moles of A and B and the volumes and then using pv=nrt to get the total pressure.
OR would i do p1v1=p2v2
and add each partial pressure to get a total pressure? I think the p1v1=p2v2 sounds more correct.
right on grams C.
But let me show you the shortcut.
A + B ==>C
10.0L + 8.60 L = ??Liters C.
Since B is the limiting reagent, then 8.6 L C will be formed.
A mol of gas occupies 22.4 L at STP; therefore, mols C = 8.6/22.4 = ??
and ?? x molar mass = grams. You get the same answer.
I think p1v2=p2v2 applies to a single gas. Since you have a mixture of two gases here; that is, A and C (you have 8.6 L C and 10-8.6 = 1.4L A I would go with pv = nRT. And you will be done with this railroad problem. These things are taxing, right? I note you are using two names interchangeable; do you ALSO have the railroad problem about the 97.1 fm radio? That one is more taxing than this one.
yes both questions are me.. haha.. i didn't want it to seem like one person was taking up all of your time.. soo i decided to use both my first and my middle name interchangeably.. sorry if I caused any confusion!
I could tell both were the same; I can see the IP address and both were the same. I love this kind of problem. And both DID take up a lot of time but I enjoyed helping you do them. But you aren't through with the fm station yet.
i used both pv=nrt and p1v1=p2v2 and they both gave 1 atm as the final P.
1 don't buy that. How did you get that using pv = nRT? I'll BET money you used the wrong volume. It isn't 10 L.
Ah but don't worry, you've helped more than just 1 person. thanks, from far away! :)
I apologize for any confusion caused earlier. In order to find the total pressure in the system, we can use the ideal gas law equation pV = nRT, where p represents the pressure, V is the volume, n is the number of moles, R is the gas constant, and T is the temperature in Kelvin.
To find the total pressure in the system, we need to add the partial pressures of A and C.
For A:
p1V1 = n1RT1
p1(1.4 L) = (0.446 mol)(0.0821 L·atm/mol·K)(273 K)
p1 = (0.446)(0.0821)(273) / (1.4) ≈ 0.087 atm
For C:
p2V2 = n2RT2
p2(8.6 L) = (0.384 mol)(0.0821 L·atm/mol·K)(273 K)
p2 = (0.384)(0.0821)(273) / (8.6) ≈ 0.098 atm
To find the total pressure, we add the partial pressures:
Total pressure = p1 + p2 ≈ 0.087 atm + 0.098 atm ≈ 0.185 atm
So the total pressure in the system is approximately 0.185 atm.
To find the answer for question b, you can use the ideal gas law equation pv = nRT.
First, calculate the moles of gas A and gas C using the volumes and conditions given in the problem.
For gas A:
nA = (1 atm)(1.4 L) / (0.0821 atm L mol^(-1) K^(-1))(295 K) = 0.0693 mol A
For gas C:
nC = (1 atm)(8.6 L) / (0.0821 atm L mol^(-1) K^(-1))(295 K) = 0.3525 mol C
The total moles of gas in the system can be found by adding the moles of A and C:
ntotal = nA + nC = 0.0693 mol + 0.3525 mol = 0.4218 mol
Now, use the ideal gas law equation to find the total pressure:
Ptotal = (ntotal)(0.0821 atm L mol^(-1) K^(-1))(295 K) / (10 L) = 1.031 atm
Therefore, the total pressure in the system will be approximately 1.031 atm.
I hope this helps! Let me know if you have any more questions.