Homework question 5
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Homework question 5
When using other reactions to calculate the standard enthalpy, how do you know what you need to multiply the above equations by to formulate the correct answer?
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Re: Homework question 5
Sort of like how we would find the K value by combining equations, we would look at common compounds (and phases) and try to manipulate the known equations to try to cancel out compounds that are on both sides of the added equation. When you multiply the stoichiometric coefficients of an equation by a common value, you would multiply the ΔH of the original equation by that value. When you add the equations together to form your final equation, you would just added the ΔH values together.
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Re: Homework question 5
Benjamin Rashti wrote:When using other reactions to calculate the standard enthalpy, how do you know what you need to multiply the above equations by to formulate the correct answer?
You multiply the enthalpy of the reactions in the case where the coefficient does not align with your final reaction and you need to cancel out the enthalpies of the products of one equation with the reactant enthalpies of another. For example, you may have
H2(g)+Cl2(g)–>2HCl(g) and you know that in your final equation, there is a 3Cl2, then you would multiply the enthalpy of the reaction by 3 and then follow all the other necessary steps needed to end up with the end reaction. Think back to how we calculated the K of one reaction when given the K value of multiple other reactions.
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Re: Homework question 5
When the coefficients in a chemical equation are multiplied by a factor, multiply the enthalpy value by the same factor. Adding individual equations gives the enthalpy of the overall equation from the sum of the individual enthalpies. Therefore, you must manipulate each individual equation and its enthalpy to produce the overall equation and the net enthalpy of reaction. This is similar to the manipulation of the K values for equilibrium reactions; however, coefficients are just multiplied by delta H, unlike for K when coefficients are treated as exponents.
Re: Homework question 5
I was trying to find the individual enthalpy for M(s) on the list provided in Achieve, but I could not find it. Does anyone know how I can get it?
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