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Topic: Confusing wording of a homework problem.  (Read 5278 times)

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Offline BuddyGoodness

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Confusing wording of a homework problem.
« on: November 20, 2006, 05:09:58 AM »
My Chem instructor is out of town for the week and this assignment is due on Wed and the sub doesn't know what the teacher is asking on the question either, if you can help me figure this out I would appreciate it:

In which of the following groupings of terms are the three terms closely related?
a)kinetic energy, energy of motion, cohesive forces
b)potential energy, energy of attraction, disruptive forces
c)kinetic energy, electrostatic interactions, disruptive forces
d)potential energy, electrostatic interactions, cohesive forces

What confuses me is kinetic energy and disruptive forces are the same thing, as is potential energy and cohesive forces.  Do you think he is asking for closely related terms that are not the same or vise versa, therein lies the problem.


There are two more problems that are also bothering me, if I can get answers for these as well I would appreciate it.

Which of the following samples of gas would have a new volume of 3.00 liters if the pressure is decreased from 3.00 atm to 1.00 atm at constant temperature.
a) 1.00 L He
b) 5.00 L CO2
c) 9.00 L H2S
d) more than one response
e) no correct response

We did not go over this at all really but from the book I gather that the formula is either V1 = V2xP2/P1 which gives me an answer that looks like C   or V1 = V2xP1/Ps who's answer looks like A


Finally: Calculate the grams of LiOH present in 3.0 mL of a 4% (m/v) LiOH solution.
a) 0.12 g
b) 0.4 g
c) 1.2 g
d) 4.0 g
I have no clue how to set this problem up.

I have no clue how to set this problem up to solve

Offline malc7067

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Re: Confusing wording of a homework problem.
« Reply #1 on: November 20, 2006, 05:31:20 AM »
For the second question, the equation is P1 x V1 = P2 x V2

initial pressure is 3x101.3kpa, final pressure is 101.3kpa, initial volume is unkown, final volume is 3

so ...

303.9 x V1 = 101.3 x 3

V1 = 1 litre

thats also for any gas, so id say its (d) because this applies for any gas

Offline malc7067

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Re: Confusing wording of a homework problem.
« Reply #2 on: November 20, 2006, 05:43:51 AM »
For the second question, when you say 4%, i presume u mean 4% by weight, so if an amount of the solution weighs 1kg, the LiOH will weigh 4% of that so 40g

if its 40g/L

you can times by 0.003 (the 3mL) which gives the weight of LiOH in 0.003L or 3mL

from this the answer is 0.12g...

Offline Borek

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Re: Confusing wording of a homework problem.
« Reply #3 on: November 20, 2006, 05:45:15 AM »
V1 = 1 litre

thats also for any gas, so id say its (d) because this applies for any gas

Calculations correct but the final reasoning faulty - there was only one gas given with the correct amount/volume.
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Offline Borek

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Re: Confusing wording of a homework problem.
« Reply #4 on: November 20, 2006, 05:46:27 AM »
from this the answer is 0.12g...

http://www.chemicalforums.com/index.php?topic=11277.0

Please stop giving answers - give a hint instead.
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Offline malc7067

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Re: Confusing wording of a homework problem.
« Reply #5 on: November 20, 2006, 06:43:51 AM »
my usual self for not reading the question fully, it says "which of the following samples of gas" and when it says d) more than one, it means more than one of a), b) or c), not another totally different answer... My fault :) Sorry for answering it

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