TPR CBT 5 PS Questions

[MedChallenge]

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Since TPR doesn't allow me to copy/paste, I'll try screenshots. Sorry I had to shrink the first one down. I tried splitting them into two separate screenshots after that one.

Passage III
#14 Why doesn't Bernoulli's equation work for this rate of effusion problem i.e. why wouldn't velocity increase when pressure is reduced?

#15 For the ideal gas law, don't we have to assume that the gas particles have no volume? So wouldn't an increase in volume and/or pressure cause it to deviate from the ideal gas law?



Passage V
#28 Didn't they draw the top view in the explanation wrong? If so, does that mean the answer should be counterclockwise?

#29 "Which of the following describes adjustments to the galvonometer that would necessarily increase its sensitivity to current?"

The answer is "Increasing both the strength of the magnetic field and the number of windings of the coil". What I've had problems with on more than one occasion is what they mean by "sensitivity". I answered the exact opposite...that decreasing both the strength of the magnetic field and the number of windings of the coil would make the galvonometer more sensitive to changes in current.

Thanks in advance!

 

[MedChallenge]

Anyone have ideas about any of these problems?

 

[loveoforganic]

14 - don't confuse macro and micromolecular systems. Gases under higher pressure move more quickly (unless I'm misremembering), and faster gases effuse more quickly.

15 is talking about the volume of the container, not the atoms

 

[MT Headed]

Passage III
#14 Why doesn't Bernoulli's equation work for this rate of effusion problem i.e. why wouldn't velocity increase when pressure is reduced?

#15 For the ideal gas law, don't we have to assume that the gas particles have no volume? So wouldn't an increase in volume and/or pressure cause it to deviate from the ideal gas law?

#14 - I wouldn't throw in bernoulli's physics equation into what is a simple general chemistry problem. The rate of effusion depends on (among other things) the partial pressure differential between the chambers. If you lower the pressure of the system, the partial pressure of A on the left goes down. The partial pressure of A on the right doesn't change, because it is basically zero.

#15 - Well, if they were ideal gases, then there wouldn't be any change in behavior by changing any of the parameters. This question is asking about real gases. A real gas deviates from an ideal gas under conditions of high pressure or low temperature. Increasing the volume would accomplish neither of these; in fact it would lower the pressure and make the real gas behavior even closer to the ideal.

 

[MT Headed]

#28 - The diagram on the solution explanation is annoying because it shows the flow of current (counterclockwise) (current always defined as the flow of positive charge) and also the flow of electrons (clockwise). Apply the right hand rule to the current flow, or the "left hand rule" (???) to the electron flow, and you will get the same answer, that the left side of the rectangle will be pushed up, and the right side of the rectangle will be pushed down.

#29 - The torque exerted on the needle is t=NIABsin(q). Increasing any of the values on the right would increase torque. You would make this instrument more sensitive if you could produce a larger torque from the same input of current, or if you prefer, if you could produce the same amount of torque with a smaller input of current. That's just the definition of being more sensitive*. Therefore increasing N, A, or B would all do the trick. You can't increase sin(q) because q is already 90 degrees.


* for example, think about what it means to be more sensitive to criticism, or more sensitive to the sun

 

[MedChallenge]

Thank you both!