Chemistry · Thermochemistry
Work through this past-paper style MCQ, then read the full explanation. Practice more chemistry questions on mMCQ with adaptive practice and topic analytics.
The net heat change in a chemical reaction is the same whether it is brought about in two or more different ways in one or several steps. This is known as:
- A
Henry's law
- B
Hess's law
- C
Joule's principle
- D
Dalton's law
Hess's Law is a fundamental principle in thermochemistry, asserting that the total enthalpy change during a chemical reaction is the same regardless of the number of steps in which the reaction is carried out, because enthalpy is a state function. This means that it depends only on the initial and final states of the system, not on the path taken.
Henry's law, Dalton's law, and Joule's principle all deal with different principles: Henry's law is about gas solubility in liquids, Dalton's law is about partial pressures in gas mixtures, and Joule's principle is about the conversion of electrical energy to heat in conductors. None of these involve the calculation of enthalpy changes in chemical reactions.
Henry's law relates to the solubility of gases in liquids and the pressure above the liquid, not to energy changes in reactions.
Hess's Law states that the total enthalpy change of a chemical reaction is the same, regardless of the number of steps or the specific pathway taken. It relies on the concept of enthalpy being a state function.
Joule's principle deals with the conversion of electrical energy into heat, specifically in resistive materials, and is not related to chemical reaction pathways.
Dalton's law pertains to the pressures of gases in a mixture, not to the enthalpy changes of chemical reactions.
Tagged under Chemistry · Thermochemistry · 2019