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How do the enthalpy of reaction bond energies compare to the enthalpy of formation in chemical reactions?
In chemical reactions, the enthalpy of reaction is the total energy change during the reaction, while bond energies are the energy needed to break or form specific bonds. The enthalpy of formation is the energy change when one mole of a compound is formed from its elements in their standard states. The enthalpy of reaction is influenced by bond energies, but it may not always directly correlate with the enthalpy of formation.
Why is an input of energy needed when forming NaCl?
The standard enthalpy of formation for NaCl solid is: -411,12 kJ/mol at 25 0C.
What best describes the enthalpy of formation of a substance?
The energy change that happens when a substance forms from its elements (APEX)
Bond enthalpy is always?
Bond enthalpy is the energy required to break one mole of a specific bond in a compound. It is always a positive value as energy is needed to break bonds.
What Reactions shows that the formation of NO2 requires 33.1 kJmol?
The formation of nitrogen dioxide (NO2) from its elemental constituents can be represented by the reaction: N2(g) + 2 O2(g) → 2 NO2(g). The enthalpy change for this reaction indicates that 33.1 kJ/mol of energy is required to form NO2. This value reflects the energy needed to break the bonds in the reactants and form the bonds in the product. Thus, the positive enthalpy change signifies that the reaction is endothermic, necessitating an input of energy for the formation of NO2.
How can one calculate enthalpy using bond energies?
To calculate enthalpy using bond energies, you need to subtract the total energy needed to break the bonds in the reactants from the total energy released when the new bonds form in the products. This energy difference represents the change in enthalpy for the reaction.
Why is the standard enthalpy formation of oxygen zero?
As for every pure element, the heat of formation of O is zero. That is because elements are the smallest constituents and are not made up of anything; therefore, no heat is needed to form pure elements from base substances, as there are no base substances to be used to form the pure elements.
How can one use bond energy to calculate the enthalpy change in a chemical reaction?
Bond energy can be used to calculate the enthalpy change in a chemical reaction by comparing the total energy needed to break the bonds in the reactants with the total energy released when new bonds form in the products. The difference between these two values represents the enthalpy change of the reaction.
What is the name of the energy needed to change a substance from a liquid to a gas?
The energy needed to change a substance from a liquid to a gas is called the enthalpy (or heat) of vaporization.
How large would the lattice energy need to be for the formation of NaCl2 to be exothermic?
The lattice energy needed for the formation of NaCl2 to be exothermic would need to be larger than the energy required to break the bonds in Na and Cl2 and smaller than the energy released when the new Na-Cl bonds are formed in NaCl2. This would result in a negative overall enthalpy change for the reaction, indicating an exothermic process.
How can one calculate the enthalpy change using bond energies?
To calculate the enthalpy change using bond energies, you need to subtract the total energy needed to break the bonds in the reactants from the total energy released when the new bonds form in the products. This calculation gives you the overall enthalpy change for the reaction.
What is the relationship between air enthalpy and the efficiency of a heating and cooling system?
The relationship between air enthalpy and the efficiency of a heating and cooling system is that the enthalpy of the air affects the amount of energy needed to heat or cool it. Higher enthalpy levels require more energy to change the temperature of the air, which can impact the efficiency of the system. In general, a heating and cooling system will be more efficient when working with air at lower enthalpy levels.
