Questions relating to heat and its relation to other forms of energy in chemistry.

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Which one really determines how people feel. Heat or temperature?

We use water to cool down some machines because water has high heat capacity, which means it takes more energy to increase 1 degree. Heat transfer occurs only when temperature is different. We cool ...
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Calculate the speed a a bullet (Thermodynamics)

A lead bullet is fired into a wooden beam and is stopped by the impact. At what speed must the bullet be travelling for it to be completely melted on impact? Neglect heating of the beam and assume the ...
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at constant volume why the change of enthalpy doesn't equal the change of heat

At constant pressure $p=\text{const.}$, change of internal energy equals heat subtract work(PV). So, $q=\Delta E - pV$. So is the the change of enthalpy. So we say at constant pressure, the change of ...
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Calculation of the enthalpy change of reactions

First, I'm a high school student and I wonder why every textbook just tells you how to set up those equations and cancel them to get the entropy change but never tells you why you can cancel the same ...
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18 views

Generally available fluid with good heat transport properties

I have designed a container which is heated up and has to heat up some tube-coils of water inside of it. This container is filled with a fluid that can help store and transfer the heat received from ...
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145 views

Mistake in Wikipedia article on fugacity?

The Wikipedia Article on Fugacity contains statement The contribution of nonideality to the chemical potential of a real gas is equal to RT ln $\phi$ Here $\phi$ is fugacity coefficient.I think ...
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31 views

How much heat is gained/released based off of equation?

Using this equation, $\ce{CaCl2(s) -> Ca^{2+}(aq) + 2Cl^{-}(aq)}$ and $\Delta H = - 325.0 \; kJ $ If you have 15.0 grams of the solid, how much heat is released or gained in kilojoules?
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33 views

how to judge a reaction exothermic or endothermic

Mix HCL and NaOH together(reactants are at the same temp) in a calorimeter. Temperature increases, and the book said it's an exothermic reaction. I don't get it. The thermometer is in the solution ...
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12 views

Can energy savings be estimated from activation energy differences?

Imagine two companies X and Y. Both companies use very similar technical equipment to carry out a biotechnological process where a chemical reaction is catalyzed by an enzyme. Company X uses an enzyme ...
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60 views

Finding the final temperature problem

What is the final temperature of water and iron if a $30g$ piece of iron at $144°C$ was dropped into a calorimeter with $40g$ of water at $20°C$? Specific heat of water is $4.184J/g°C$ Specific heat ...
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56 views

Is this endo or exothermic?

$$\ce{4Fe + 3O2 -> 2Fe2O3(s) + 1625kJ}$$ This should be endothermic because the energy is in the product. However, if the equation is viewed from the perspective of the reactant, it is ...
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17 views

Is the end of a cigarette on fire when lit?

Is the end of a cigarette on fire when it is lit? Or is it smoldering? Is there a chemical difference between the two?
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Calculating the partition function based on molar heat capacity

Given the molar heat capacity of a partition function as a function of temperature, how would one determine the partition function? Say the molar heat capacity = $\alpha T^2$
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37 views

How much heat (in J) is required to produce 2.0L of $N_2(g)$ at 77.36 K and 1.0 atm?

The only thing that is given is: The enthalpy of vaporization for $N_2(l)$ is 5.56 kJ/mol. There aren't any examples similar to this problem in the textbook. I only know how to get energy using: ...
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17 views

Enthalpy change of a constant pressure process

In the question, we were expected to find "enthalpy change of a constant pressure process where internal energy of gas is increased $x\ \text{kJ}$ of energy and $y\ \text{kJ}$ of work is done by the ...
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74 views

Proving RTln($a_i$) equal to non PV work done by system,where $a_i$ is activity

We know that chemical potential is defined as ${\mu}_i={\mu}_i^{standard}+RT\ln(a_i)$. Here $a_i$ is the activity of $i^\text{th}$ component of solution. In case of gases instead of $a_i$ it is $f_i$ ...
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35 views

Delta H of reaction and finding delta h of components?

$\Delta H$ for the reaction below is -126 KJ $$\ce{2Na2O2(s) + 2 H2O(l) ->4 NaOH(s) + O2 (g)}$$ What is the amount of heat released by the reaction of 25.0 gram of $\ce{Na2O2}$ with water?
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Heat capacity and finding Delta T? [closed]

When a reaction was carried out in a bomb calorimeter 2.710 kJ of heat was released. If the initial temperature was 19.897 °C and the total heat capacity of the system was 989.0 J / °C, what is the ...
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23 views

What kind of equilibrium constant we use for Gibbs free energy and Van't Hoff equation?

We know that Gibbs free energy is same as negative of 8.314 times temperature in Kelvin times natural logarithm of equilibrium constant, or: Then, we also know Van't Hoff equation, like: (R in ...
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Why is adiabatic process isentropic? [migrated]

I have read that adiabatic process is isentropic because there is no heat exchange in an adiabatic process and thus no change in entropy. But my question is - Even in adiabatic process, work can be ...
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1answer
15 views

Thermochemistry Delta T?

An equation of heat is s * m * delta T. I know that delta T can be in either Celsius or Kelvin. However, one thing that confuses me is how the units cancel if delta T is in Celsius. How does this ...
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21 views

Change in pressure or volume of molten salt

I am doing a project in which I fill a cylinder with a volume of $636cm^2$ (made of stainless steel) with molten salt: 60% Sodium Nitrate ($NaNO_3$) and 40% Potassium Nitrate($KNO_3$). The container ...
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29 views

Heat capacity question

The specific heat capacity of liquid water is $4.18 \, \text{J} \, \text{K}^{-1} \, \text{g}^{-1}$. Calculate the energy required to heat $1.0 \, \text{mol}$ of water from $298 \, \text{K}$ to $363 \, ...
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36 views

Does covalent character increase or decrease bond strength?

I am a bit confused on one hand covalent character increases the bond dissociation enthalpy (i.e. more energy is needed to be put in) and on the other it lowers the melting point of Al2O3 to a value ...
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What happens to water under high pressures without possibility of escape?

Knowing very little about the nature of water, wondering how it might behave at the centre of a planet or centre of an another massive gravitational body. Could water take such pressures or might it ...
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23 views

How to estimate the dielectric constant of a liquid?

Are there any approximate relationships between the (static) dielectric constant of a liquid and properties of the individual molecules? For example, suppose I know the polarizability and dipole ...
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1answer
24 views

What is the energy change of ethene reacting with hydrogen gas?

$\ce{CH2CH2(g) + H2(g) -> CH3CH3(g)}$ Using this table, source: http://www.kentchemistry.com/images/links/Kinetics/TB08_003.GIF ...
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34 views

Covalent character and ionic dissociation enthalpy?

I am a bit confused does covalent characteristic within a bond increase or decrease its strength as i have found two counter examples: firstly covelent character increases the enthalpy of dissociation ...
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90 views

Conceptualizing Multiple Equilibria

Take the reaction: $$ (1) \; \ce{A + B <=>X + Y}, \; K_1=\frac{[X][Y]}{[A][B]} $$ Now assume that X isomerizes to Z according to: $$ (2) \; \ce{X <=> Z}, \; K_2=\frac{[Z]}{[X]} $$ We can ...
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51 views

Why isn't ΔG equal to zero for this equilibrium reaction?

In the reaction $\ce{E(g) <=> P(g)}$ at 25°C, equilibrium is reached when the pressure of the product is 0.100 that of the reactant. What is $\Delta G$ in joules? Using $\Delta G = \text{RT} ln ...
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85 views

T is the temperature of what?

In equation of gibbs free energy change $\Delta G = \Delta H-T\Delta S$,is T system's or surrounding's temperature? Edit:Oh sorry I am not clear earlier now I get clear question.I know we have to ...
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103 views

Hess's Law/Enthalpy of Formation problems?

How do I solve problems where I'm asked for $\Delta H^\circ_f$ and given $\Delta H^\circ_f$ values for equations with the involved elements? For example: Find the $\Delta H^\circ_f$ of the following ...
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29 views

How to trace an Energy Time diagram?

I'm looking for data to create a simple graph of an exothermic or endothermic reaction but can't find any. Could someone help me with some enough data to create a Energy(time) simple graph.
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191 views

Approximate time for pure water pH to equilibrate in open air?

I'm a complete non-chemist, so I don't know how to calculate this, or even what to google for (my searches yielded esoteric research papers). I'm doing some hobby experiments, and I'd like to know ...
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What is the heat required to melt this ice cube?

I am need of help with this question: 18 g is one mole. (a) I guess you meant to 0 degrees C? So, 70.391 x 20 = 1408 J (b) 6.01 kJ (c) 180 g is 10 moles. It would take about 15kJ to cool all of ...
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1answer
54 views

Why does the equilibrium constant depend on the temperature but not on pressure and concentration?

According to my textbook (and intuitively) certain changes when the aforementioned 3 variables are altered occur in accordance with Le Chatelier's Principle. However, what I don't understand is what ...
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35 views

Standard reference for thermodynamic properties for octane

where can I find thermodynamics properties for octane at saturated Temp.$T_s$? I need this properties or where can i find all ? $$liquid-density=\rho_l=?$$ $$vapor-density=\rho_v=?$$ ...
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37 views

problem with partial pressures

This is a question I solved in class: At 35 degrees, $\ce{N_2O_4}$ is 15% dissociated in a flask at a pressure of 1.2 atm. Calculate $K_p$ Equation: $$\ce{N_2O_4(g)<=>2NO_2 (g)}$$ ...
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Equations to Support Argument in Protein Physics

I'm studying for a test in Protein Physics and my lecturer says we should know why proline and glycine are not seen in alpha helices and that we should use equations in order to support our arguments. ...
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37 views

Why is ionization energy measured in gaseous phase?

When I looked up the definition of ionization energy, it says:- it is the energy required to remove one electron from the shell to infinity in an atom in gaseous state. Why is it measured in ...
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How could I create a machine that as rapidly as possible creates greenhouse gases from air?

For a very large-scale project, I am trying to create a greenhouse gas demonstration device, which rapidly produces greenhouse gases from atmospheric air using only electricity, or any chemical ...
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63 views

Thermodynamic stability of benzene ring

In learned that when benzene undergoes hydrogenation, $208KJ$ of energy is given off and thus $152KJ$ less energy than what would be given off if Kekule's structure was correct. My confusion is that ...
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30 views

Is there a function for finding the pressure of an explosion? [duplicate]

Is there a function $P(t)$ that lets you calculate the pressure of an explosion: $\ce{2H2 + O2 -> 2H2O}$ given these variables? $V \text{ (volume)}$ $n \text{ (moles of hydrogen and oxygen ...
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About the T-S diagram

Suppose we have a T-S diagram of some vapor thermodynamic cycle , say the rankine cycle , and we are interested for example in the composition of the liquid and the vapor in the middle of the ...
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Chemical Potential of Idea gas?

Let's say we have a mixture of different ideal gases. I found that the chemical potential of a single component of the mixture is $$\mu_{i}=g_{i}^{0}+Ln(\frac{f_{i}}{P_{ref}})$$ where $f_{i}$ is the ...
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Polymers with no molecular mass distribution?

What sort of ideal conditions are required - theoretically - to conduct polymerization reactions to make all the macromolecules end up with exactly the same molecular mass, just like the products in ...
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53 views

Enthalpy of Zinc and Sulfur Reaction

I was working on my homework which was to write a description of what would occur if zinc and sulfur reacted and what steps would a scientist have to make in order to make them react. When I ...
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51 views

Thermal decomposition of calcium carbonate

Thermal decomposition of calcium carbonate. In general, we heat $\ce{CaCO3}$ to temperature of approximately 825°C it decomposes into calcium oxide and liberates carbon dioxide gas:* $$\ce{CaCO3} ...
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23 views

Relation between c and compressibility

We know that $c^2=\frac{\partial p}{\partial ρ}$ The adiabatic compressibility is defined as: $\beta_S=-\frac{1}{V}\frac{\partial V}{\partial p}$ such that the subscript "S" stands for "adiabatic" ...
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55 views

How to calculate ring strain energy

Series A and B below can be viewed in two different ways to annulate an ethano bridge onto four-, five-, and six-membered rings. Using the $\Delta H_f^\circ$ values given (in kcal/mol), how can one ...