What is Enthalpy Change ?

What is Enthalpy Change ?
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: The matte energy that is obtained by combining the product of pressure and volume with the internal energy of a system is called enthalpy. Enthalpy is expressed by H. Therefore - enthalpy = internal energy + pressure ের volume of the system or , where H = E + PV , E = internal energy P = pressure , V = volume. It can never be diagnosed. However, the change in the enthalpy of a system can be accurately determined. Change of enthalpy = [product enthalpy - reactive enthalpy]
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What is meant by entropy driven reaction? How can the reaction with positive change of enthalpy and entropy be made entropy driven?

Description : What is meant by entropy driven reaction? How can the reaction with positive change of enthalpy and entropy be made entropy driven?

Last Answer : Ans.The free energy change of a reaction is given by ΔG = ΔH - TΔS For a reaction to be spontaneous, ΔG should be -ve. If both ΔH and ΔS are positive ΔG can be -ve if TΔS>ΔH in magnitude. Thus, entropy ... is low, TΔS should be greater than ΔH (ii) If ΔS is small, T should be so large that TΔS>ΔH.

Does anyone know of a link for help on solving the change in enthalpy?

Description : Does anyone know of a link for help on solving the change in enthalpy?

Last Answer : Wikipedia explains it well. http://en.wikipedia.org/wiki/Enthalpy

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"If different processes are used to bring about the same chemical reaction, the enthalpy change is same for all of them". This is __________ law. (A) Hess's (B) Kirchoff's (C) Lavoisier and Laplace (D) None of these

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The enthalpy change when ammonia gas is dissolved in water is called the heat of (A) Solution (B) Formation (C) Dilution (D) Combustion

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If two pure liquid constituents are mixed in any proportion to give an ideal solution, there is no change in (A) Volume (B) Enthalpy (C) Both (A) & (B) (D) Neither (A) nor (B)

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Pressure-enthalpy chart is useful in refrigeration. The change in internal energy of an ideal fluid used in ideal refrigeration cycle is (A) Positive (B) Negative (C) Zero (D) Infinity

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The change in __________ is equal to the reversible work for compression in steady state flow process under isothermal condition. (A) Internal energy (B) Enthalpy (C) Gibbs free energy (D) Helmholtz free energy

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Last Answer : (C) Gibbs free energy

The product of efficiency & heat transferred to the working fluid is? a. Net temperature change b. Net work done c. Net enthalpy change d. None of the mentioned

Description : The product of efficiency & heat transferred to the working fluid is? a. Net temperature change b. Net work done c. Net enthalpy change d. None of the mentioned

Last Answer : b. Net work done

Fire tube boilers are those in which a) Flue gases pass through tubes and water around it b) Water passes through the tubes and flue gases around it c) Work is done during adiabatic expansion d) Change is enthalpy

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Last Answer : a) Flue gases pass through tubes and water around it

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Description : Water tube boilers are those in which a) Flue gases pass through tubes and water around it b) Water passes through the tubes and flue gases around it c) Work is done during adiabatic expansion d) Change is enthalpy

Last Answer : b) Water passes through the tubes and flue gases around it

Entropy is the measure of:  a. The internal energy of a gas  b. The heat capacity of a substance  c. Randomness or disorder  d. The change of enthalpy of a system

Description : Entropy is the measure of:  a. The internal energy of a gas  b. The heat capacity of a substance  c. Randomness or disorder  d. The change of enthalpy of a system

Last Answer : Randomness or disorder

An ideal gas is compresses isothermally. The enthalpy change is  a. Always negative  b. Always positive  c. zero  d. undefined

Description : An ideal gas is compresses isothermally. The enthalpy change is  a. Always negative  b. Always positive  c. zero  d. undefined

Last Answer : zero

The change that the system that undergoes from one equilibrium state to another is known as  a. oath  b. process  c. enthalpy change  d. entropy change

Description : The change that the system that undergoes from one equilibrium state to another is known as  a. oath  b. process  c. enthalpy change  d. entropy change

Last Answer : process

Which of the following occurs in a reversible polytrophic process?  a. Enthalpy remains constant  b. Internal energy does not change  c. Some heat transfer occurs  d. Entropy remains constant

Description : Which of the following occurs in a reversible polytrophic process?  a. Enthalpy remains constant  b. Internal energy does not change  c. Some heat transfer occurs  d. Entropy remains constant

Last Answer : Some heat transfer occurs

A state occurs in isentropic process  a. The change in entropy is 0  b. The change in entropy is 1  c. The change in enthalpy is 0  d. The change in enthalpy is 1

Description : A state occurs in isentropic process  a. The change in entropy is 0  b. The change in entropy is 1  c. The change in enthalpy is 0  d. The change in enthalpy is 1

Last Answer : The change in entropy is 0

Regardless of the process, the change in enthalpy firm moles of ideal gas is  a. Heat  b. Enthalpy  c. Entropy  d. Density

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Last Answer : Heat

An adiabatic process in which there is no change in system enthalpy but for which there is a significant decrease in pressure is called _____.  A. Isochoric process  B. Isobaric process  C. Throttling process  D. Quasistatic process

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Last Answer : Throttling process

“The enthalpy change for any chemical reaction is independent of the intermediate stages, provided the initial and final conditions are the same for each route.” This statement is known as:

Description : “The enthalpy change for any chemical reaction is independent of the intermediate stages, provided the initial and final conditions are the same for each route.” This statement is known as:  A. Dulong’s Law  B. Dalton’s Law  C. Hess’s Law  D. Petit Law

Last Answer : Hess’s Law

In an isothermal process,  A. there is no change in temperature  B. there is no change in enthalpy  C. there is no change in internal energy  D. all of these

Description : In an isothermal process,  A. there is no change in temperature  B. there is no change in enthalpy  C. there is no change in internal energy  D. all of these

Last Answer : Answer: D

If heat be exchanged in a reversible manner, which of the following property of the working substance will change accordingly  (a) temperature  (b) enthalpy  (c) internal energy  (d) entropy  (e) all of the above.

Description : If heat be exchanged in a reversible manner, which of the following property of the working substance will change accordingly  (a) temperature  (b) enthalpy  (c) internal energy  (d) entropy  (e) all of the above.

Last Answer : Answer : d

Change in enthalpy in a closed system is equal to heat transferred if the reversible process takes place at constant  (a) pressure  (b) temperature  (c) volume  (d) internal energy  (e) entropy.

Description : Change in enthalpy in a closed system is equal to heat transferred if the reversible process takes place at constant  (a) pressure  (b) temperature  (c) volume  (d) internal energy  (e) entropy.

Last Answer : Answer : a

Change in enthalpy of a system is the heat supplied at  (a) constant pressure  (b) constant temperature  (c) constant volume  (d) constant entropy  (e) N.T.P. condition.

Description : Change in enthalpy of a system is the heat supplied at  (a) constant pressure  (b) constant temperature  (c) constant volume  (d) constant entropy  (e) N.T.P. condition.

Last Answer : Answer : a

What is quenching heat or quenching enthalpy ?:?

Description : What is quenching heat or quenching enthalpy ?:?

Last Answer : amount of heat generated during the formation of 1 mol of water by diluting 1 mol H + of a given acid at a temperature of 25 ° C is called quenching heat or quenching enthalpy . The value of the propagation heat of all strong acids and strong bases is equal to - 57.34 kj .

What is combustion heat or combustion enthalpy ?

Description : What is combustion heat or combustion enthalpy ?

Last Answer : The change in enthalpy that occurs when a basic or compound substance is completely burned in oxygen at a certain temperature and 1 atm pressure is called combustion heat or combustion enthalpy. The change ... combustion heat or proof combustion enthalpy of that substance. It is expressed by H ° C.

What is the composition of the compound called heat or structure enthalpy ?

Description : What is the composition of the compound called heat or structure enthalpy ?

Last Answer : The change in enthalpy that occurs during the production of one mole from the constituent elements of a compound in the state of proof is called the formation of heat or formation enthalpy of the compound. The enthalpy ... a temperature of 25 ° C and a pressure of 1 atm is expressed by ∆ H ° f .

What is Lettuce Enthalpy ?

Description : What is Lettuce Enthalpy ?

Last Answer : Lettuce enthalpy is the combination of a gaseous atom's transformation enthalpy method with the basic component of an atom under certain conditions.

The order of Ionization enthalpy between following atoms is?

Description : The order of Ionization enthalpy between following atoms is?

Last Answer : B, Tl, Ga, Al and In. Ans.B>Tl>Ga> Al> In.