Methyl tert-butyl ether (MTBE) is prepared by reaciton of methanol (l) (ΔH°f = -239.2 kJ/mol) with 2-methyl-propene (g), according to the requation Calculate ΔH°f in kJ/mol for 2-methylpropene
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First, we need to understand that the heat of formation (ΔH°f) is the heat change that results when one mole of a compound is formed from its elements at standard conditions. For elements in their standard state, the heat of formation is zero.
The heat of reaction (ΔH°rxn) is the sum of the heats of formation of the products minus the sum of the heats of formation of the reactants. In this case, we are given the heat of formation for methanol and we are asked to find the heat of formation for 2-methylpropene. The reaction is: methanol (l) + 2-methylpropene (g) -> MTBE (l).
We can write the heat of reaction as: ΔH°rxn = ΔH°f (MTBE) - [ΔH°f (methanol) + ΔH°f (2-methylpropene)]. We are given ΔH°f (methanol) and we need to find ΔH°f (2-methylpropene).
To find ΔH°f (2-methylpropene), we need to rearrange the equation to solve for it: ΔH°f (2-methylpropene) = ΔH°f (MTBE) - ΔH°rxn - ΔH°f (methanol).
Finally, substitute the given values into the equation to find the heat of formation for 2-methylpropene. Remember to keep track of the signs for each term in the equation.
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Key Concepts
Here are the essential concepts you must grasp in order to answer the question correctly.
Enthalpy of Formation (ΔH°f)
The enthalpy of formation (ΔH°f) is the change in enthalpy when one mole of a compound is formed from its elements in their standard states. It is a crucial concept in thermodynamics, as it allows chemists to calculate the energy changes associated with chemical reactions. The values are typically given in kJ/mol and can be used to determine the overall energy change of a reaction.
Hess's Law states that the total enthalpy change for a reaction is the same, regardless of the number of steps taken to complete the reaction. This principle allows for the calculation of enthalpy changes by using known ΔH°f values of reactants and products. By applying Hess's Law, one can derive the ΔH°f for 2-methylpropene by manipulating the reaction equations involving MTBE and methanol.
Stoichiometry involves the calculation of reactants and products in chemical reactions based on the balanced chemical equation. It is essential for determining the relationships between the quantities of substances consumed and produced. In this context, understanding the stoichiometric coefficients in the reaction between methanol and 2-methylpropene is necessary to accurately calculate the ΔH°f for 2-methylpropene.
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