# Questions tagged [heat]

For questions about heat - a form of transfer of energy from one body to another or from one body to its surroundings. Also see these tags: [thermodynamics], [enthalpy], [energy], [temperature].

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### Calculating Enthalpy Change from Calorimetry [closed]

What calculating the enthalpy change of a reaction, for example 5g of CaCl2 dissolving in 100 mL of water, is m the mass of water or the mass of water plus the mass of the salt. q = (105g)(4.18)T or q ...
39 views

### Does heat increase the hydrolysis of urea hydrochloride?

The preparation of ammonium chloride by reacting urea with HCl produce urea hydrochloride the reaction take too much time to get ammonium chloride depending on ratios. So can heat increase the ... 32 views

### What do they mean with temperature in the formula for enthalpy?

I'm studying enthalpy and I'm having a real hard time trying to conceptualize it. I can do the exercises and know the formulas but I feel like I lack an understanding of what it actually is. One of my ...
107 views

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### Why is enthalpy and not heat released by system used while calculating entropy of surroundings?

While finding the sum of change in entropy of the universe and thus defining Gibbs free energy, why is the change in entropy of surrounding the negative of enthalpy of the system divided by the ...
1 vote
201 views

### Relation between enthalpy and internal energy for chemical reaction at constant volume

Question The combustion of benzene(l) gives $\ce{CO2(g)}$ and $\ce{H2O(l)}.$ Given that the heat of combustion of benzene at constant volume is $\pu{-3263.9 kJ mol-1}$ at $\pu{25 ^\circ C}$; heat of ...
664 views

### Does all fire only emit light on its outermost shell?

This question is about light emission, which may overlap with physics, but I am most interested in combustion and types of flame (incandescence, petrochemical fuel flames, nuclear ractions). Consider ...
1 vote
49 views

### Cooling down from −78 °C to −88 °C without cryogenics

Say I have a gas cylinder with nitrous oxide and cool it down to −78 °C with dry ice. Is there an endothermic process/reaction that would extract the remaining heat from $\ce{N2O}$ and bring it down ...
1 vote
105 views

### What did I do wrong in my temperature change calculations?

I am doing an online assignment where I am being asked to find temperature change but there is something wrong in my calculations as I am getting the answer wrong. Can someone help me figure out where ...
170 views

### Cinnabar decomposition by heating optional method?

Is it possible to decompose cinnabar into $\ce{Hg}$ and $\ce{S}$ instead of $\ce{Hg + SO2}$ with roasting and heating. What conditions need to be satisfied in the new method?
100 views

### In a heating curve, when it is plateau, where does all the energy go since the temperature does not get higher? [closed]

So between the change of phases within the matter(solid liquid gas), the temperature reaches a plateau, no matter how much heat you add to it, it just stays the same. Where did all those energy go?
358 views

### Why does higher temperature affect the rate of electrolysis?

I understand that more heat energy= higher rate of electrolysis, but can someone explain using higher-level terms why this occurs and if there are any theories or rules that explain this?
80 views

### What is non toxic to fish, has a low freezing point, and floats on water?

I am looking for a liquid that floats on water that will prevent the water from freezing (or at least slow it down). The application would be a small area (less than a square foot). It has to be non-...
From the first law of thermodynamics, $\mathrm{d}U = đQ + đW$, where $\mathrm{d}$ represents an exact differential and $đ$ an inexact differential. Exact differentials correspond to state functions ...