EK Chemistry question

[Wassupboy]

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Hey all, I could use a little help

Qn 1.
Substance A has greater heat capacity than B. Which of the following is most likely true?

1) A has larger molecules than B
2) B has lower boiling point than A
3) At same temperature, B molecules move faster than those of A
4) A has more methods of absorbing energy than B

All the choices seem wrong to me. But 1) and 3) are basically saying the same thing. Correct answer is 4) but I don't understand how having a greater heat capacity means that it has more methods???

Qn 2.
In a free adiabatic expansion, a real gas is allowed to spread to twice its original volume with no energy transfer from the surroundings. Which is false?

1) No work is done
2) Increased potential energy between molecules results in decrease KE
3) Entropy increases
4) Gas loses heat

I chose 1. Work should be done if there is change in volume right? 4 also makes sense as it is not losing heat. Correct answer is 4.

Thanks for the help

 

[ToldYouSo]

Qn 1) It means that there are basically more paths, bonds or interactions that have to be broken before the molecules kinetic energy changes. In water for example, there are hydrogen bonds that require energy to be weakened or broken before the water molecules can move around more vigorously. Compare that to hydrogen sulfide which has no hydrogen bonds and therefore is one less "method" to bypass with energy.

Qn 2) The gas is expanding without any input of energy from the surroundings. 1 is true because the volume of the container doesn't change, so work can't be done. Yes the gas itself is expanding but the container it's in isn't. Think of the rock analogy, if you try pushing a 2000 pound rock and it doesn't move you haven't done any work despite putting in energy. 4 is false (thus the right answer) because the internal energy of the gas remains constant. The temperature of the gas can't change because there's no energy transfer.

 

[Wassupboy]

Qn 1) It means that there are basically more paths, bonds or interactions that have to be broken before the molecules kinetic energy changes. In water for example, there are hydrogen bonds that require energy to be weakened or broken before the water molecules can move around more vigorously. Compare that to hydrogen sulfide which has no hydrogen bonds and therefore is one less "method" to bypass with energy.

Qn 2) The gas is expanding without any input of energy from the surroundings. 1 is true because the volume of the container doesn't change, so work can't be done. Yes the gas itself is expanding but the container it's in isn't. Think of the rock analogy, if you try pushing a 2000 pound rock and it doesn't move you haven't done any work despite putting in energy. 4 is false (thus the right answer) because the internal energy of the gas remains constant. The temperature of the gas can't change because there's no energy transfer.

Thanks for the reply mate!

I understand the reasoning for qn 2 now. I missed the free expansion part haha

And for qn 1, I initially interpreted it as absorbing energy through conduction, convection etc and not in terms of the types of bonds that have to be broken. Makes sense now.