In a generic chemical reaction involving reactants A and B and product C and D,

Question

In a generic chemical reaction involving reactants A and B and product C and D, aA + bB rightarrow cC + dD, the standard enthalpy delta H_rxn degree of the reaction is given by H_rxn degree = c delta H_f degree(C) + d delta H_f degree(D) - a delta H_f degree(A) - b delta H_f degree(B) Notice that the stoichiometric coefficients a, b, c, d, are an important part of this equation. This formula is often generalized as follows, where the first sum on the right-hand side of the equation is a sum over the products and the second sum is over the reactants: delta H_rxn degree = sigma_products n delta H_f degree - sigma_reactants m delta H_f degree where m and n represent the appropriate stoichiometric coefficients for each substance. What is delta H_rxn degree for the following chemical reaction? CO_2(g) + 2KOH(s) rightarrow H_2O(g) + K_2CO_3(s) You can use the following table of standard heats of formation (delta H_f degree) to calculate the enthalpy of the given reaction. Express the standard enthalpy of reaction to three significant figures and include the appropriate units.

Explanation / Answer

The enthalpy of the reaction mentioned in the question can be calculated by subtracting the total enthalpy of formation of both the reactants CO2 and KOH from that of products that is H2O and K2CO3.

So delta H is given as :

Delta H = [ ( -241.8) + (-1150) ] - [ (-393.5) + ( 2x -424.7) ]

Delta H = -148.9 KJ

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