Topscore Test 3 problems

[critterbug]

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First inquiry:

Problem # 59

What is density of PF3 at STP

ANSWER: 3.22

However, I calculate 3.98



Second Enquiry:

Problem # 54

What is the value of the rate constant for a reaction that has a half-life of 1.5 hours?

 

[croco]

for #1, always round .0821 to .1. so 1(88)/27.3=3.22

#2 -- 1.5=ln2/k or k=.693/1.5 or roughly .47

if these are wrong explain them 2 me. thx

 

[critterbug]

Well, I hope there aren't any natural log calculations on the REAL DAT

But, that looks right.

 

[critterbug]

However, on the first one, where did you get 27.4? Shouldn't the denominator be 22.4

At STP 1 mole of gas = 22.4 L

 

[croco]

well i have 27.3
the equation for density is D=P(MM)/RT when R=.1 and T=273 so .1*273=27.3 btw MM=molecular mass

 

[croco]

hiya Mo!!

 

[croco]

btw critter, I would read the chapter on nuc chemistry again if i were you. learn half life well. i had like 6 questions where I had to use the natural log to find various things

 

[Mo007]

Hey Croco

I envy you man... you done with the DAT, getting interviews... geeez, I am all stuck up in here with Exam Krackers (thanks for the recommendation). 5 days untild DAT, I already missed RED SOX games in the play-offs.

I feel ready though, I have a good feeling that I can do this test with blind-folds (right!).

Good luck to everyone.