portlander

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1) A tick bird on a rhinosaurus is an example of what type of symbiotic relationship?

A. Commensalism
B. Mutualism
C. Parasitism
D. Saprophytism
E. Insectism

Answer key says 'B'. I am not an ecology person, but I put 'A' because commensalism means one organism gets a benefit while the other is neither harmed nor helped. In what way is a rhino benefiting from the 'tick bird'? Is that information something I would have had to know beforehand?

2) When 14.250 moles of PCl5 gas is placed in a 3.00 liter container and comes to equilibrium at a constant temperature, 40.0% of the PCl5 is decomposed
PCl5 (g) ------------> PCl3 (g) + Cl2 (g)
What is the value of Kc??

A. (1.896)^2 / (2.854)
B. (2.854)^2 / (1.898)
C. (3.800)^2 / (2.854)
D. (2.854)(1.896) / (3.800)
E. None of these

The answer key says 'A'. I know that Kc is = to
[PCl3][Cl2] / [PCl5], and that concentrations of PCl3 and Cl2 are equal, and that the concentrations should be measured in atms, but I cannot make the numbers work out. How do you figure out the pressures??

Thanks so much for whoever can help!

Taking my DAT 3 weeks from today!!!
 

nycdoc

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The tick bird is eating the ticks therefore the rhino is benefitting because it no longer has ticks. The bird is getting food, the rhino is getting groomed. Mutual relationship=mutualism
 
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portlander

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Thanks so much!!

I have one more:

The 1H NMR of which of these compounds will show only 2 singlets?

A. CH3-CH2-O-CH2-CH3
B. H3C-O-{phenyl}-O-CH3

The answer is 'B'. I can see how both of these might get two singlets, but I haven't had Orgo in a long time. Why is 'A' wrong?
 

DesiDentist

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think of the tick question in this way.

A tick is a parasite, so if a tick bird is eating the parasite it is helping the rhino. Thus both are being helped.

DesiDentist
 

ItsGavinC

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portlander,

For the Organic question, you can apply the "n+1" rule in a general manner. That is, "n" Hydrogen atoms are going to give n+1 peaks.

You can instantly see that CH3-CH2-O-CH2-CH3 will have more than "only two singlets".
 

DATMATT

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I believe the statement that

"CH3-CH2-O-CH2-CH3 will have more than only two singlets". Should be clarified. It will not have any singlets. It will have 2 quartets and 2 triplets.

Matt
 

sjdent

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Portlander,

You know what one of the happiest (and scariest) things about taking the DAT is?

Happiest: knowing you'll never have to remember facts from crappy subjects like G. Chem.

Scariest: knowing it's that easy to forget facts from crappy subjects like G. Chem. I swear I've forgotten all that stuff, from O. Chem to G. Chem. Yikes.
 

DesiDentist

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tell me about it. I never paid attention in Ochem, now I'm crapping my pants. I just crammed and that was the biggest mistake of my life...but I still did decently.

To all of those who haven't taken ochem, but planning to. Take your time and absorb this material like a sponge. You will thank yourself later. Trust me.

DesiDentist
 
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