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Calculate Enthalpy Change Decomposition Hydrogen Peroxide
Calculating the enthalpy change of hydrogen peroxide decomposition
Between heaven and earth, the change of all things is related to the conversion of energy. Today, we want to study the enthalpy change of hydrogen peroxide decomposition, which is a key issue in chemistry and is related to the field of thermochemistry.
Hydrogen peroxide, its decomposition reaction formula is: $2H_ {2} O_ {2} (l) \ longrightarrow 2H_ {2} O (l) + O_ {2} (g) $. To know this reaction enthalpy change, we need to rely on the principles of thermochemistry and related data.
The method of covering thermochemistry often relies on the data of enthalpy formation to calculate the reaction enthalpy change. Enthalpy formation is the enthalpy change of a molar compound formed from the most stable element at a specific temperature and pressure. The enthalpy of formation of $H_ {2} O_ {2} (l) $is $\ Delta H_ {f} ^ {\ ominus} (H_ {2} O_ {2}, l) = -187.8\ kJ/mol $, $H_ {2} O (l) $is $\ Delta H_ {f} ^ {\ ominus} (H_ {2} O, l) = -285.8\ kJ/mol $, and oxygen $O_ {2} (g) $is the most stable element, and its enthalpy of formation is $\ Delta H_ {f} ^ {\ ominus} (O_ {2}, g) = 0\ KJ/mol $.
According to the reaction enthalpy change formula $\ Delta H ^ {\ ominus} =\ sum_ {product} n_ {product}\ Delta H_ {f} ^ {\ ominus} (product) -\ sum_ {reactant} n_ {reactant}\ Delta H_ {f} ^ {\ ominus} (reactant) $, for hydrogen peroxide decomposition reaction:
$\ Delta H ^ {\ ominus} = [2\ times\ Delta H_ {f} ^ {\ ominus} (H_ {2} O, l) + 1\ times\ Delta H_ {f} ^ {\ ominus} (O_ {2}, g) ] - [2\ times\ Delta H_ {f} ^ {\ ominus} (H_ {2} O_ {2}, l) ] $
Substitute the enthalpy of formation data for each substance to obtain:
$\ Delta H ^ {\ ominus} = [2\ times (-285.8\ kJ/mol) + 1\ times0\ kJ/mol] - [2\ times (-187.8\ kJ/mol) ] $
$=[ - 571.6\ kJ/mol + 0\ kJ/mol] - [-375.6\ kJ/mol] $
$= -571.6\ kJ/mol + 375.6\ kJ /mol $
$= - 196\ kJ/mol $
, the enthalpy of hydrogen peroxide decomposition becomes $- 196\ kJ/mol $, indicating that the reaction is exothermic, and heat is released during the reaction.
Between heaven and earth, the change of all things is related to the conversion of energy. Today, we want to study the enthalpy change of hydrogen peroxide decomposition, which is a key issue in chemistry and is related to the field of thermochemistry.
Hydrogen peroxide, its decomposition reaction formula is: $2H_ {2} O_ {2} (l) \ longrightarrow 2H_ {2} O (l) + O_ {2} (g) $. To know this reaction enthalpy change, we need to rely on the principles of thermochemistry and related data.
The method of covering thermochemistry often relies on the data of enthalpy formation to calculate the reaction enthalpy change. Enthalpy formation is the enthalpy change of a molar compound formed from the most stable element at a specific temperature and pressure. The enthalpy of formation of $H_ {2} O_ {2} (l) $is $\ Delta H_ {f} ^ {\ ominus} (H_ {2} O_ {2}, l) = -187.8\ kJ/mol $, $H_ {2} O (l) $is $\ Delta H_ {f} ^ {\ ominus} (H_ {2} O, l) = -285.8\ kJ/mol $, and oxygen $O_ {2} (g) $is the most stable element, and its enthalpy of formation is $\ Delta H_ {f} ^ {\ ominus} (O_ {2}, g) = 0\ KJ/mol $.
According to the reaction enthalpy change formula $\ Delta H ^ {\ ominus} =\ sum_ {product} n_ {product}\ Delta H_ {f} ^ {\ ominus} (product) -\ sum_ {reactant} n_ {reactant}\ Delta H_ {f} ^ {\ ominus} (reactant) $, for hydrogen peroxide decomposition reaction:
$\ Delta H ^ {\ ominus} = [2\ times\ Delta H_ {f} ^ {\ ominus} (H_ {2} O, l) + 1\ times\ Delta H_ {f} ^ {\ ominus} (O_ {2}, g) ] - [2\ times\ Delta H_ {f} ^ {\ ominus} (H_ {2} O_ {2}, l) ] $
Substitute the enthalpy of formation data for each substance to obtain:
$\ Delta H ^ {\ ominus} = [2\ times (-285.8\ kJ/mol) + 1\ times0\ kJ/mol] - [2\ times (-187.8\ kJ/mol) ] $
$=[ - 571.6\ kJ/mol + 0\ kJ/mol] - [-375.6\ kJ/mol] $
$= -571.6\ kJ/mol + 375.6\ kJ /mol $
$= - 196\ kJ/mol $
, the enthalpy of hydrogen peroxide decomposition becomes $- 196\ kJ/mol $, indicating that the reaction is exothermic, and heat is released during the reaction.
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