G Chem Problems..

[DMD to Be]

---

Members do not see this ad.

Gas A is at 30 degrees C and gas B is at 20 degrees C. Both gases are at 1 atmosphere. What is the ratio of the volume of 1 mole of gas A to 1 mole of gas B?
A. 1:1
B. 2:3
C. 3:2
D. 303:293
E. 606:293


Which of the following elements has an ionic radius that is larger than its atomic radius?
A. Na
B. K
C. Mg
D. Al
E. Cl


If one mole of a gas originally at STP is placed in a container where the pressure is doubled and the absolute temperature (measured in K) is tripled, what is the new volume in liters?
A. 2.2 L
B. 5.6 L
C. 7.5 L
D. 11.2 L
E. 33.6 L



Answers, respectively: D, E, E


Explanations needed. Thanks so much...

 

[ernest1284]

can someone explain #2.....
i know about atomic radii but, does this have to do with Al being a metal?

 

[DrBowtie]

E (Cl) is the only anion. More electrons equals bigger cloud.

 

[joonkimdds]

Gas A is at 30 degrees C and gas B is at 20 degrees C. Both gases are at 1 atmosphere. What is the ratio of the volume of 1 mole of gas A to 1 mole of gas B?
A. 1:1
B. 2:3
C. 3:2
D. 303:293
E. 606:293


Which of the following elements has an ionic radius that is larger than its atomic radius?
A. Na
B. K
C. Mg
D. Al
E. Cl


If one mole of a gas originally at STP is placed in a container where the pressure is doubled and the absolute temperature (measured in K) is tripled, what is the new volume in liters?
A. 2.2 L
B. 5.6 L
C. 7.5 L
D. 11.2 L
E. 33.6 L



Answers, respectively: D, E, E


Explanations needed. Thanks so much...

I am kinda tired cuz i just came back from VA beach, and it's 1:18am, but let me just answer very quickly.

First of all, what u need to know is that "At STP, a mole of gas has 22.4 Liter of volume" and ideal gas rule "PV=nRT"

now let's look at the first problem.
it's about gas A vs. gas B so we can make it into
PV=nRT of A vs. PV=nRT of B
so far so good?
both of them have ATP so same temperature and pressure for A and B
so we can get rid of T and P for A and B, so far so good?
R is ideal gas constant and thus we can get rid of R from each side.
now we are left with
V=T of A vs. V = T of B, got it?
oh and don't forget to change Celcius into Kelvin.
20 C = 20+273.15 = 293.15 Kelvin
30 C = 30+273.15 = 313.15 Kelvin
so substitute it into the equation and we get
V=293.15 vs. V=313.15
in other words
V/293.15 = V/313.15
cross multiply~ and u get
293.15Vb = 313.15Va
I think u made a typo of writing 303 instead of 313.
my explanation look kinda long and complicated but i hope you could understand what i wrote.

now let's look at the third problem since i need periodic table to solve 2nd problem and i m kinda tired to look at it.
volume is proportional to temperature and inversely proportional to pressure.
it means if temperature doubles, volume doubles.
if pressure doubles, volume halves.
I hope this gives u an idea of what proportional and inversely proportional mean.
anyway pressure doubled so volume is halved.(it's it's inversely proportional)
temperature trippled so the volume has to be trippled (since it's proportional)
as i said in the beginning, volume is 22.4L at STP for a mole of gas.
in conclusion, 22.4L X 3 x 1/2 = 33.6L.

I hope my explanation helped u. I sux at explaning.

 

[DMD to Be]

I am kinda tired cuz i just came back from VA beach, and it's 1:18am, but let me just answer very quickly.

First of all, what u need to know is that "At STP, a mole of gas has 22.4 Liter of volume" and ideal gas rule "PV=nRT"

now let's look at the first problem.
it's about gas A vs. gas B so we can make it into
PV=nRT of A vs. PV=nRT of B
so far so good?
both of them have ATP so same temperature and pressure for A and B
so we can get rid of T and P for A and B, so far so good?
R is ideal gas constant and thus we can get rid of R from each side.
now we are left with
V=T of A vs. V = T of B, got it?
oh and don't forget to change Celcius into Kelvin.
20 C = 20+273.15 = 293.15 Kelvin
30 C = 30+273.15 = 313.15 Kelvin
so substitute it into the equation and we get
V=293.15 vs. V=313.15
in other words
V/293.15 = V/313.15
cross multiply~ and u get
293.15Vb = 313.15Va
I think u made a typo of writing 303 instead of 313.
my explanation look kinda long and complicated but i hope you could understand what i wrote.

now let's look at the third problem since i need periodic table to solve 2nd problem and i m kinda tired to look at it.
volume is proportional to temperature and inversely proportional to pressure.
it means if temperature doubles, volume doubles.
if pressure doubles, volume halves.
I hope this gives u an idea of what proportional and inversely proportional mean.
anyway pressure doubled so volume is halved.(it's it's inversely proportional)
temperature trippled so the volume has to be trippled (since it's proportional)
as i said in the beginning, volume is 22.4L at STP for a mole of gas.
in conclusion, 22.4L X 3 x 1/2 = 33.6L.

I hope my explanation helped u. I sux at explaning.

Thanks for your explanations, they helped. But, there was not a typo in the first problem. The correct answer has 303 in the numerator. 🙂

 

[DMD to Be]

accidentally reposted....

 

[DMD to Be]

I still don't completely understand the first one though...any one else care to explain?

 

[Notoriousjae]

I still don't completely understand the first one though...any one else care to explain?

V1/T1=V2/T2 <-- charles law
Let V1=1 mole of gas A and V2=1 mole of gas B
T1 of gas A= 273+30=303 and T2 of gas B= 273+20=293
V1/303=V2/293--> 1/303=1/293 or simply can be written as 303=293 or 303/293 so the ratio ends up to be 303:293 answer is D

joonkim made a mistake in addition and apparently you didnt catch it either and i thought iwas bad at math 🙂
also btw you dont use ideal gas law like joon said instead you have to apply charles law. he ended up making the whole damn thing so confusing with all that unnecessary PV=nRT crap lol

 

[Notoriousjae]

btw i was just curious but where are you getting these questions from?

 

[DMD to Be]

btw i was just curious but where are you getting these questions from?

http://www.esnips.com/web/dat-stuff
Those questions came from GChem Test 1. It is all really good practice. By the way, thanks for your explanation. Much much more clear and understandable. 🙂

 

[planetmrmr]

Shouldnt it be 293:303??

 

[Notoriousjae]

http://www.esnips.com/web/dat-stuff
Those questions came from GChem Test 1. It is all really good practice. By the way, thanks for your explanation. Much much more clear and understandable. 🙂

👍 😀

 

[joonkimdds]

V1/T1=V2/T2 <-- charles law
Let V1=1 mole of gas A and V2=1 mole of gas B
T1 of gas A= 273+30=303 and T2 of gas B= 273+20=293
V1/303=V2/293--> 1/303=1/293 or simply can be written as 303=293 or 303/293 so the ratio ends up to be 303:293 answer is D

joonkim made a mistake in addition and apparently you didnt catch it either and i thought iwas bad at math 🙂
also btw you dont use ideal gas law like joon said instead you have to apply charles law. he ended up making the whole damn thing so confusing with all that unnecessary PV=nRT crap lol

Oh Crap! I can't even do addition right! 😱
I am so worried about my math section, i better start studying more hours!!!