Question

For the reaction, $ {{C}_{2}}{{H}_{4\left( s \right)}}+3{{O}_{2}}\to 2C{{O}_{2\left( g \right)}}+2{{H}_{2}}{{O}_{\left( l \right)}};\text{ }\Delta U=-1415kJ. $ Then $ \Delta H $ at $ 27{}^\circ C $ is?
(A) $ -1410kJ. $
(B) $ -1420kJ. $
(C) $ +1420kJ. $
(D) $ +1410kJ. $

Answer 1

Hint :We know that the change in enthalpy of a reaction is the amount of heat released or being absorbed as the reaction takes place. We can calculate the change in enthalpy in different ways depending on the specific situation. The formula here we have to use is $ \Delta H=\Delta E+\Delta ngRT $ .

Complete Step By Step Answer:
Enthalpy can be defined as the energy or the heat content of the total system. Enthalpy is one of the most crucial and important factors in thermodynamics (the study of the interrelation between heat and other forms of energy). The measurement of change in enthalpy is important for understanding the total mechanics of the chemical reaction. Any chemical (or biochemical) reaction involves an exchange of energy in any form amongst the substance undergoing that reaction and their surroundings.
The total enthalpy change during a chemical reaction is molecularly equal to the amount of heat energy that went into the system from the surroundings or went into the surroundings from the system. In totality, the first law of thermodynamics holds true during every reaction that no amount of heat is either created or destroyed during any reaction.
For the given chemical reaction; $ \Delta H=\Delta E+ \Delta ngRT $
Here $ T=27{}^\circ C=300K $ , $ \Delta ng=2 $ since we have two byproducts, $ R=8.314 $ and $ \Delta E=-1415. $
Now by just substituting the values in formula we get;
 $ \Delta H=\left[ -1415 \right]+\left[ \left( -2 \right)\times 8.314\times 300 \right]=-1420KJ $

Note :
Remember that as we know that enthalpy is an energy-like property that has dimensions of energy. It is mainly measured in joules or ergs. It is found that there are several factors that affect the enthalpy of reaction, these are the temperature of the system, the concentration of the reactants and the partial pressure of the gases if any are involved.