Chemistry: First principle of thermodynamics

It looks like there is a mistake in the answer key. It should state that options A and B are both false. So in summary, the first principle of thermodynamics states that E=q+w, where q represents heat flow and w represents work done. In this problem, q=-17 kJ, meaning that heat flows from the system to the surroundings. Therefore, the process is endothermic, as it absorbs heat from the surroundings. However, the answer key states that only option B (false) is incorrect, when in fact, both options A and B are false.
  • #1
yecko
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Homework Statement


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Homework Equations


First principle of thermodynamics: E=q+w

The Attempt at a Solution


E=q+w=-17+21=4kJ>0
∴Endothermic (absorb heat from surrounding)

(a) false (from surrounding to the system)
(b) false (does work by surrounding)
(c) true
(d) true

the answer states only option b is false... why option a is true?
Thank you very much!
 
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  • #2
q=-17 kJ means that heat flows from the system to the surroundings. So "a" is not false.

And why are you using E=q+w=-17+21=4kJ>0 to say that
∴Endothermic (absorb heat from surrounding)?
 
  • #3
I see. thanks.
 
  • #4
It is impossible for only option B to be false. If B is false E is also false.
 
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  • #5
mjc123 said:
It is impossible for only option B to be false. If B is false E is also false.
Good catch.
 

FAQ: Chemistry: First principle of thermodynamics

What is the first principle of thermodynamics in chemistry?

The first principle of thermodynamics, also known as the law of conservation of energy, states that energy cannot be created or destroyed, only transferred or converted from one form to another.

How does the first principle of thermodynamics apply to chemical reactions?

In chemical reactions, the first principle of thermodynamics means that the total energy of the reactants must be equal to the total energy of the products. This is known as the principle of energy conservation.

What is the difference between heat and temperature in the context of the first principle of thermodynamics?

Heat refers to the transfer of energy from a hotter object to a cooler object, while temperature is a measure of the average kinetic energy of the particles in a substance. The first principle of thermodynamics deals with the total energy of a system, including both heat and other forms of energy.

How does the first principle of thermodynamics relate to enthalpy?

Enthalpy is a measure of the total heat content of a system. The first principle of thermodynamics states that the change in enthalpy in a chemical reaction must be equal to the heat exchanged between the system and its surroundings, assuming constant pressure.

What is an example of the first principle of thermodynamics in action?

An example of the first principle of thermodynamics in action is a combustion reaction, where the chemical energy stored in the reactants is converted into heat and other forms of energy. The total energy of the reactants is equal to the total energy of the products, in accordance with the first principle of thermodynamics.

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