# Questions tagged [enthalpy]

A thermodynamic state function describing the total energy content of a system.

420 questions
Filter by
Sorted by
Tagged with
2k views

### Mathematical basis of why enthalpy of mixing is 0 for ideal gas

For this case, let's say there are two identical chambers connected by a small tube, constant pressure and temperature. There's a closed valve that separates the two chambers. Within the chambers ...
65 views

### Enthalpy: when and how does it vary? [closed]

I have been looking for a physical explanation for entropy and enthalpy variations. An example would be the air system of a vehicle, where people say we have a strong enthalpy and entropy variations ...
11k views

### Calculating standard enthalpy of reaction, which reactant to choose for the amount of substance

For example, this reaction: $$\ce{2NaOH + H2SO4 -> Na2SO4 + H2O}$$ Suppose both concentrations are $1\ \mathrm{mol\ l^{-1}}$ (standard condition). There is $0.02\ \mathrm{mol}$ ($20\ \mathrm{cm^3}$...
2k views

### What non-toxic non-water substances have a freezing point very close to water's?

I was linked to a Kickstarter for a cooling ball to be placed in drinks which claims with constant marketing hyperbole how much it relies on "Phase Change" ! which is a neat concept and seems not ...
101 views

1k views

Given the standard enthalpy of formation of $\ce{AgNO3(aq)} = \pu{-99 kJ/mol}$ and the standard enthalpy of formation of $\ce{Ag+(aq)} = \pu{+105 kJ/mol}$, what's the standard heat of formation of $\... 2answers 13k views ### When is it okay to use$Q=mc\Delta T$, is this equation only for calorimetry questions? When is it okay to use$Q=mc\Delta T$, is the equation only for calorimetry questions? When a question talks about heat how do I know if i'm measuring$\Delta H$or Q? 2answers 4k views ### What defines the specific enthalpy of atomization? [duplicate] 1 mol of$\ce{F2}$is turned into$\ce{2F}(atoms). Is this the specific enthalpy of atomization, or two times that? 3answers 15k views ### Why is heating increasing the solubility of sodium hydroxide? \begin{align} \ce{NaOH &-> Na+ + OH-} & \Delta H^\circ &= \pu{-44.51 kJ/mol} \end{align} The dissolution of sodium hydroxide in water is an exothermic process, and so, according to Le ... 1answer 10k views ### Enthalpy Calculations, Heat of Formation/Combustion I just don't understand how to do these and would really appreciate your help. 1) Ammonium dichromate decomposes in a reaction when heated. Calculate the heat transferred for the decomposition of 53.... 1answer 151 views ### How can oxygen atoms suddenly appear on the product side of an equation? The question states the following equation: $$\ce{C(s) + 2H2(g) -> CO2(g) + 2H2O}$$ And then asks you to calculate the enthalpy change for it, given enthalpies of combustion. The stated values ... 3answers 5k views ### Methane seems to dissolve more readily in cold water. Why? When you are diluting air in the system and/or properly evacuating it, you must consider water temperature. Methane is completely dissolved in water at 42 degrees Fahrenheit (5.5 C) but can be ... 2answers 180 views ### What is the energy package released to the outside world? Consider a chemical reaction where two different particles form another one $$\ce{O + O_2 -> O_3}$$ I find it confusing how this can be an exothermic process. How to picture the release of+\...
So there is the standard formation enthalpy $\Delta H^0_f$ and there is also formation entropy. Are there more (independent) quantities? What about the heat capacity? Is there a general theoretical ...
Is it possible for a dissolution reaction of the form $$\ce{X(s) ->[solvent] X (solv)}$$ or $$\ce{M_mX_x (s) ->[solvent] m M^x+ (solv) + x X^m- (solv)}$$ to be endothermic, i.e. \$\Delta_\...