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Quick Chemistry Question

Aabid

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I'm kinda stuck on this and my friend and I were debating over this.

 

Question is...

 

 

Heptain and octane are found in gasoline. Heptane has a boiling point of 98 degrees and octane has a boiling point of 125 degrees. If a mixture of heptane and octane is distilled, what will happen?

 

A) Heptane will be the distillate. Octane will be the residue.

B) Heptain will be the residue. Octane will be the distillate.

C)Nothing will happen since heptanes (the s is prob. a spelling mistake) and octane cannot be separated by distillation.

D)Both the heptanes and he octane will become distillate.

E)Heptane will undergo a chemical change to form octane at higher temperatures.

 

 

Friend said A) because since Heptane boils faster, it will condense faster.

This seems retarded cause it doesn't say the temp. it will get distilled at. And they both seem gases.

 

I said D) because they are both gases and after a certain temp, they will both condense.

 

I'm not really sure though.

 

 

Another one I have which is kinda more of wording issue.

 

 

A 32 gram sample of sulfur has a yellow appearance and melts at 118.9C and boils at 444.6C. If exposed to silver, sulfur has the potential to tarnish the precious metal. A 32 gram sample of sulfur can be combined with 2 grams of hydrogen gas to form 34 grams of the "rotten" eggs smelling compund hydrogen sulfide. Sulfur does not dissolve in water however it does burn with a blue flame.

 

How many characteristic quantitative physical properties about sulfur are mentioned in the above message?

 

 

A) 0

B) 1

C) 2

D) 3

E) more than 3

 

I'm stuck between D and E cause...

32 gram of sulfur

Melting point

Boiling Point

but it says 32 grams again... confusing mannn

 

 

btw a quick question again....

 

is insulin a pure substance? :o

 

 

I've done enough research and worked like 3 hours and this whole set of questions. (More than these 3 but these 3 have stumped me (kinda)).

Thanks :D



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Boiling point means when it turns into a gas from a liquid.

Change it state right?

 

 

Also requirements for what?

 

So for first 1 it is D.

 

Chem is my favorite subject. <3

 

The second one is just mind games for me. >.< Not even sure what to put lol.

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I'm gonna say go with D for the first one. I took AP Chem last year and I see 3 quantitative physical properties. I don't think saying 32 grams twice would count as two.

 

However, maybe turning that into a mole of S counts as 1? I don't really know, but I highly doubt they will count that.

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I give up

I meant to requirements are stated in the text book for simple distillation. ..<

Lemme go check again.

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Requirement for what the temperature difference needs to be for a proper separation.

 

second question sucks lol

I don't think they've already explored the hilarious world of exceptions-to-separation-methods, partial vapour pressures and saddle azeotropes in 1st year chemistry.

 

But yeah, it's not like the first question is decent either. Had it been water and ethanol it would have made a great trick question. :D

 

Although, if it's 1st year chemistry, A sounds like the most logical answer. "It doesn't say the temp. it will get distilled at" isn't a valid objection, because distillation - by definition - is the separation of two (or more) chemicals, and it ends as soon as all chemical A is separated (and the temperature of the residue begins to rise again). Think of it as filtration: you don't need to know the diametre of the filter as long as you know that it will separate water and sand.

 

What lilshu says about "check what boiling point means" is:

Heptane has a boiling point of 98 degrees and octane has a boiling point of 125 degrees. [...] they both seem gases.
Given that room temperature is 20-25 degrees (we're using Celsius, remember?), they sure as hell aren't gases at all.

 

 

Second question: two quantitative properties, therefore C. The quantity of the chemical isn't a property, as it changes with...erm...quantity? Melting point and boiling point are properties, as they are always the same (assuming constant pressure)

 

is insulin a pure substance?
Is it a solution? Is it a colloid? Is it a suspension?

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Arianna, on , said:

 

I don't think they've already explored the hilarious world of exceptions-to-separation-methods, partial vapour pressures and saddle azeotropes in 1st year chemistry

I was thinking they may have vaguely described that compounds with similar boiling points are inseparable, without going into detail.

 

Quote

 

Second question: two quantitative properties, therefore C. The quantity of the chemical isn't a property, as it changes with...erm...quantity? Melting point and boiling point are properties, as they are always the same (assuming constant pressure)

http://en.wikipedia....t_of_properties

 

 

Woah so Arianna was wrong. >.<

Ethanol is gas so that would both become distillate as well.

Arianna, on , said:

 

I don't think they've already explored the hilarious world of exceptions-to-separation-methods, partial vapour pressures and saddle azeotropes in 1st year chemistry

I was thinking they may have vaguely described that compounds with similar boiling points are inseparable, without going into detail.

 

Quote

 

Second question: two quantitative properties, therefore C. The quantity of the chemical isn't a property, as it changes with...erm...quantity? Melting point and boiling point are properties, as they are always the same (assuming constant pressure)

http://en.wikipedia....t_of_properties

 

 

Its grade 11 btw, not university. >.<

 

 

OK

looking through my notes I found that fractional distillation is to separate a mixture with various components that have various boiling pts.

But we are mainly focusing on simple distillation.

so that counts as distillation.

ATM, I'm nailing my first answer on D. I've been researching and it seems that when they separate, we can all make them come out at different layers. (WUT... I don't even know how this makes sense lol)

The second is D or E for sure as mass, boiling point, and melting point are all on the list.

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Quote

 

looking through my notes I found that fractional distillation is to separate a mixture with various components that have various boiling pts.

If that's verbatim from your notes, you need to pay much, much more attention in class.

 

Yeah that is verbatim from my notes (If that makes sense in context)

If you don't mind, can you tell me where I am going wrong. I just know that heptane and octane are different boiling pts which apply to my notes.

 

 

And do you have any tips for class and doing well in school in general. (If you don't mind) I really want to improve to 90s this year.

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Ok I do all that except...

Writing Notes again and work problems.

Is it really worth writing notes again?

 

 

Tbh we rarely have any idea what we will be doing next class cause its high school. >.<

 

Also, how should I study for tests? Do I start studying a while back? (I do this but I never know how far back I should start studying)

I try to review notes on a regular bases though.

 

BTW what grade/what year university are you on. You seem like a baws. :P

So for the first question, I will stick with your answer.

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I assume that by pure substance you mean a substance that cannot be separated into smaller components.

 

Insulin is a dimer having an A chain (21 aa) and a B chain (30 aa), which are joined by two disulfide bonds (well, it's actually three bonds, but only two join both chains together) . These bonds can be broken by a reductive agent such as beta-mercaptoethanol. Therefore, insulin isn't a pure substance because it can be broken down into smaller components.

 

Aside from this, proteins can be broken down into their corresponding amino acids by a process called proteolysis (which is just a special type of hydrolysis . This process can be done by digestive enzymes (such as pepsin, tripsin and chymotripsin) or by intracellular structures such as lysosomes or proteasomes.

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