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Verified answer
Heat is required to make the reaction occur.
Wiki User
∙ 11y ago
Dilim
No, an exothermic reaction releases heat energy to the surroundings, resulting in a negative change in enthalpy (ΔH < 0). A positive change in enthalpy (ΔH > 0) indicates an endothermic reaction, which absorbs heat energy from the surroundings.
Wiki User
∙ 15y agoThis is actually trickier than it sounds, because it depends on the particular conventions you're using. I studied thermodynamics in two different classes, one chemistry and and one physics, at the same time ... and the two textbooks used different conventions for the sign of delta-H. The physics book used a positive delta-H to mean that you could get work OUT of the system (exothermic), the chemistry book used a positive delta-H to mean you had to put work INTO the system (endothermic). The best thing is to review your textbook and see which convention they use.
Wiki User
∙ 8y agoTypically, exothermic reactions have negative enthalpy, But this may not always necessarily be the case.
To prove this we say that H=U+PV and U=Q+W (H=enthalpy, U=internal energy, P=pressure, V=volume, Q=heat, W=work).
H=U+PV
Substitute for U (see above)
H=Q+W+PV
Take the differential of dH:
dH=dQ+dW+d(PV)
Plug in for dW with dW=-P(deltaV)) (this is true for a ideal gas expanding against constant external pressure)
dH=dQ-P(deltaV)+d(PV)
Take the derivative of d(PV) using the chain rule
dH=dQ-P(deltaV)+P(deltaV)+V(deltaP)
Cancel like terms
dH=dQ+V(deltaP)
At constant pressure (which is what is normally observed in almost all naturally occurring environments the pressure is constant so the V(deltaP) term is 0 (change in volume is zero) and therefore dH=dQ. So in this case, if Q is negative so is enthalpy. However, if are at constant volume conditions (example: a bomb calormiter) where the pressure can change it may be possible to have a V(deltaP) term that is greater than the negative Q (indicating the reaction is exothermic while still giving you a positive enthalpy.
Example: dQ=-1000J (Exothermic process) V=(5L) deltaP=2atm
dH=dQ+V(deltaP)
dH=-1000J+10L*atm=-1000J+1013.25J=13.25... (10Latm=1013.25J)
dH is positive while the process is exothermic. I understand these conditions are extreme and unlikely, but they are being used to illustrate a point - mathematically, and potentially IRL, it is plausible to have an exothermic process with a positive change in enthalpy.
Wiki User
∙ 13y agoyes
Wiki User
∙ 12y agonegative
What is true of the enthalpy reaction?
The enthalpy of a reaction is a measure of the heat energy exchanged with the surroundings at constant pressure. A negative enthalpy change indicates an exothermic reaction, where heat is released. A positive enthalpy change indicates an endothermic reaction, where heat is absorbed.
Which is true of the enthalpy of a reaction?
Its value does not depend on which reactions are added.
What is the enthalpy of reaction apex's?
The enthalpy of reaction, denoted as ΔH, is the heat absorbed or released during a chemical reaction. It is specific to each reaction and can be positive (endothermic) or negative (exothermic). The value of enthalpy of reaction for a specific reaction can be calculated experimentally or using thermodynamic data.
What kind of enthalpy change favors a spontaneous reaction?
For a spontaneous reaction, the overall change in enthalpy should be negative (exothermic). This means that the products have a lower enthalpy than the reactants, releasing energy in the form of heat.
What does a negative H tell about a reaction?
A negative change in enthalpy (ΔH) indicates that a reaction is exothermic, meaning it releases heat to its surroundings. This suggests that the products have less energy than the reactants, leading to a decrease in enthalpy during the reaction.
What does it mean if the change in enthalpy value for a chemical reaction is positive?
Change in enthalpy value for a chemical reaction is positive is because,there loose of electron(s) in the reaction, and that will change the enthalpy of that particular element from negetive,neutral to positive.
Is vaporisation an exothermic or endothermic process?
Any reaction categories into exothermic and endothermic based upon change in enthalpy of reaction. If difference in enthalpy of product and reactant comes positive value then it is termed as endothermic and if it is negative value then exothermic reaction. Usually, vaporisation is considered as exothermic due to release in energy.
Are titrations endothermic or exothermic?
In thermometric titration the reaction enthalpy is used to follow the chemical reaction. I guess it dépends on the titration reaction it can be exothermic or endothermic. ΔHr (molar heat of reaction) negative (indicating an exothermic reaction) or positive (indicating an endothermic reaction
What is process that involves absorption of heat?
endothermic reaction a positive enthalpy.
Is polymerization endothermic or exothermic?
Polymerization can be either endothermic or exothermic, depending on the specific monomers and reaction conditions involved. Some polymerization reactions release energy (exothermic), while others may require energy input (endothermic) to overcome activation barriers.
What kind of enthalpy change favors a spontaneous reaction?
For a spontaneous reaction, the overall change in enthalpy should be negative (exothermic). This means that the products have a lower enthalpy than the reactants, releasing energy in the form of heat.
What is the sign of ΔT in an endothermic reaction?
ΔH is the enthalpy of the reaction and will be positive in an endothermic reaction and negative in an exothermic reaction.ΔT designates a change in temperature. T2-T1 = ΔTOften the change in temperature will be negative for an endothermic reaction.
In an exothermic reaction is the energy of the products higher or lower than that of the reactants?
In an exothermic reaction the energy of the products is less than that of the reactants.
How do you know if an enthalpy change diagram is endothermic or exothermic?
In an endothermic reaction, the products have higher enthalpy than the reactants, leading to a positive overall change in enthalpy. In contrast, in an exothermic reaction, the products have lower enthalpy than the reactants, resulting in a negative overall change in enthalpy. This information can be determined by looking at the direction in which the energy levels are changing on the enthalpy change diagram.
What type of reaction is exothermic reaction?
The reaction in which energy is being released, and the overall energy change (enthalpy) is negative.
What is heat of reaction and enthalpy of reaction?
The heat of reaction is the amount of heat energy released or absorbed during a chemical reaction. Enthalpy of reaction is the change in enthalpy (heat content) that occurs during a reaction at constant pressure. Both are measures of the energy changes that take place during a chemical reaction.
Does an exothermic reaction contain more chemical energy than reactants?
depends , if the reaction is endothermic or exothermic. if the reaction is endothermic , the energy needed to break the bonds is greater than the energy that forms bonds.and to break bonds you need thermal energy , meanwhile forming bonds gives off energy. now if the reaction is exothermic the energy given off the bonds form are greater than the enrgy needed to break them. you know if the reaction is exothermic or endothermic because exothermic have a negitave delta next to d eqn.while endothermic have a positive delta.
