Simple EK 1001 gen chem question

[golgiapparatus88]

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"A naturally-occurring sample of which of the following has the smallest density at room temperature?"

a) argon
b) chlorine
c) phosphorus
d) sulfur.

Now the answer is A but density is mass/volume. All are gases so shouldn't it be phosphorus?

The question before it had carbon, fluorine, nitrogen and oxygen. The answer is nitrogen because it has the lowest MW.

What am I missing?!

Thanks in advance.

 

[sv3]

"A naturally-occurring sample of which of the following has the smallest density at room temperature?"

a) argon
b) chlorine
c) phosphorus
d) sulfur.

Now the answer is A but density is mass/volume. All are gases so shouldn't it be phosphorus?

The question before it had carbon, fluorine, nitrogen and oxygen. The answer is nitrogen because it has the lowest MW.

What am I missing?!

Thanks in advance.

there is no more of an explanation? God that is terrible.
only thing that comes to mind is the "naturally occuring" phrase b/c C has a lighter mw than N and yet they said Nitrogen for the previous question. Thus, carbon in its natural phase at room temp might be quatra-atomic (4 carbons?) and Nitrogen diatomic, hence Nitrogen is lower. not sure how to make sense otherwise. Regarding of the actual size of the atom, all gases at STP will take up the same volume (22.4L).

For the current question, first thing that came to mind is this: IS Argon diatomic? if not, that could be why its A. Not sure why else. Hopefully someone else can chime in. IF you find out, let me know please!

sv

 

[golgiapparatus88]

the explanation is "based on the logic of the previous question, you might think that the answer should be "B." But be careful: chlorine is a diatomic gas and has a MM of 71g/mol while argon is monatomic and has a molar mass of 40g/mol."

I still don't understand because P and S aren't diatomics either and P has a MM of 30g/mol. What the hell Examkrackers!

 

[sv3]

P and S are not diatomic......they are polyatomic!!
Which means even heavier. There is your answer. I hate these questions as they require quite a bit of memorization and i find them hard to narrow down. Anyway, there you go. Noble gases are all monoatomic for future reference and it helps to know the diatomic ones but I've never encountered having to know what is polyatomic and to what extent.

 

[Vanguard23]

I looked up the MSDS for Phosphorus and it's boiling point is 100C(the question states room temp). The only conclusion that I can come to is that it's a liquid they expect you to somehow know that. Either way, I remember the question and despised it since it pretty much takes what you learned and beats you over the head with it for no reason.

 

[golgiapparatus88]

P and S are not diatomic......they are polyatomic!!
Which means even heavier. There is your answer. I hate these questions as they require quite a bit of memorization and i find them hard to narrow down. Anyway, there you go. Noble gases are all monoatomic for future reference and it helps to know the diatomic ones but I've never encountered having to know what is polyatomic and to what extent.

Thank you so much! I hate these questions because I feel like I should know them all.. either way, i guess that's why the EK 1001 books are good..by the end of tonight I'll have no problem with any of these on the real test!

 

[sv3]

Thank you so much! I hate these questions because I feel like I should know them all.. either way, i guess that's why the EK 1001 books are good..by the end of tonight I'll have no problem with any of these on the real test!

Interesting.....I have them (the Ek) books but really dont have time to do those questions - ive been jsut sticking to TPR. Hopefully I'm not missing out.........

 

[golgiapparatus88]

Interesting.....I have them (the Ek) books but really dont have time to do those questions - ive been jsut sticking to TPR. Hopefully I'm not missing out.........

Do you use TPR hyperlearning series? I'm buying them from someone on Monday and I'm really excited to use those as well in my studies.

 

[sv3]

Do you use TPR hyperlearning series? I'm buying them from someone on Monday and I'm really excited to use those as well in my studies.

Yup - i use their content review and their Science workbook which as TONS of questions. Once you see it, you'll see why i can't use Ek too....no time! I want to but just can't. TPR has great explanations too.

I'm on my last science (bio) and really liked them for the first three. I am very rusty (been 8 years since i did science) so need TPR and Ek was just not cutting it.

I always worry when I see questions like the one you posted but at the end of the day, I just choce TPR cause i understood their explanations best. I hear they are more difficult than the average AAMC which is always nice to hear too.

gluck

 

[loveoforganic]

Just to be clear.... Phosphorus and sulfur, at standard conditions, are both solids! I have no idea where they're getting their information. Between argon and chlorine - argon is a noble gas, and thus monoatomic. Chlorine is a halide and thus diatomic. Chlorine therefore has both a higher MW and more surface area (linear structure as opposed to spherical), and thus more area to interact with other chlorine molecules.

 

[sleepy425]

Just to be clear.... Phosphorus and sulfur, at standard conditions, are both solids! I have no idea where they're getting their information. Between argon and chlorine - argon is a noble gas, and thus monoatomic. Chlorine is a halide and thus diatomic. Chlorine therefore has both a higher MW and more surface area (linear structure as opposed to spherical), and thus more area to interact with other chlorine molecules.

actually, it was just the OP who said that phosphorus and sulfur were also gases, the question didn't imply that they all had to be gases. it just said which is least dense.

 

[chemtopper]

whenever density or boiling point or some other physical constant is discussed ,than always think and apply it on molecules
.a) argon ---Ar
b) chlorine ---Cl2
c) phosphorus----P4
d) sulfur.---S8
So all of them are nonpolar and attracted by London Dispersion forces.We know london dispersion forces increases with molar mass. Here density will be minimum for Ar because of its lowest molar mass and lowest attractive forces.So less no of atoms per unit volume and hence less density .

 

[chemtopper]

The question before it had carbon, fluorine, nitrogen and oxygen. The answer is nitrogen because it has the lowest MW.



Apply same concept-
Carbon has tetrahedral covalent linkage in which many atoms are bonded with each other.
N2
F2
O2
So here also N2 has the lowest molar mass and lowest london dispersion forces.

 

[Biochemistry]

whenever density or boiling point or some other physical constant is discussed ,than always think and apply it on molecules
.a) argon ---Ar
b) chlorine ---Cl2
c) phosphorus----P4
d) sulfur.---S8
So all of them are nonpolar and attracted by London Dispersion forces.We know london dispersion forces increases with molar mass. Here density will be minimum for Ar because of its lowest molar mass and lowest attractive forces.So less no of atoms per unit volume and hence less density .

-the best thing to do with this problem is to use the ideal gas equation which is PV=nRT
where P is standard presssure usually at 1 atm
V is the gas volume
n is the number of moles
R is the gas constant
T is the room temperature (standard room temp. vary cold climates have 25 degrees celsius while warmer have 32 to 26..
rearranging PV=nRT into n/V=P/RT (the unit of this is moles/cubic meter to transform this into kg/cubic meter multiply with the molecular weight, MW)
so the density is Density=(n/V)MW=(P/RT)(MW)....
elements having the lowest MW will have the lowest density....