Question

Measurements show that the enthalpy of a mixture of gaseous reactants increases by 215. kJ during a certain chemical reaction, which is carried out at a constant pressure. Furthermore, by carefully monitoring the volume change it is determined that -155. kJ of work is done on the mixture during the reaction.

Calculate the change in energy of the gas mixture during the reaction. Round your answer to 2 significant digits.


Is the reaction exothermic or endothermic?

Answer 1

1. The change in energy is 60KJ or 6.0 × 10^1 KJ

2. Endothermic reaction

Step-by-step explanation:

The Enthalpy (ΔU) for the mixture is given as 215kJ and the workdone (W) on the mixture is - 155KJ. Hence, the change in the energy (ΔH) ofthe mixture is computed using the equation below:

ΔH = ΔU + w

Where,

ΔH= Change in energy

ΔU= Enthalpy change

W= workdone

Therefore ΔH is:

ΔH= 215 kJ + (-155Kj)

ΔH= 60 KJ

Therefore, the change in energy is 60KJ or 6.0 × 10^1 KJ

The value is positive so it is an endothermic reaction.

An endothermic reaction happens when the energy used to break the bonds in the reactants is higher than the energy given out when bonds are formed in the products. This means that the entire reaction takes in energy, hence there is a temperature decrease in the surroundings. Endothermic reactions cannot happen spontaneously. Work is usually done in order to get these reactions to occur. When endothermic reactions absorb energy, a temperature drop is measured by the reaction.