The temperature of a sample of liquid water changes from 50°C to 30°C. Which statement best explains the change that must
happen at the molecular level?
A)The molecules move more quickly and their average kinetic energy increases
B)The molecules move more slowly and their average kinetic energy decreases
C)The molecules move more quickly and their average kinetic energy decreases
D)The molecules move more slowly and their average kinetic energy increases

The statement which best explains the change that must happen at the molecular level is below:

Explanation:

The molecules move more slowly and their average kinetic energy decreases

B: The molecules move more slowly and their average kinetic energy decreases.

Explanation:

took the test

answer: the enthalpy of the overall chemical reaction is +87.88 kj or +88 kj.

according to hess's law, the overall enthalpy of a reaction is the difference between the sum of enthalpy values of all the products and the sum of enthalpy values of all the reactants.

δh(reaction) = ∑nδh(products) - ∑nδh(reactants)

δh(reaction) = [δh +δh] - [δh]

δh(reaction) = [1(-287.02) + 1(0) ] - [1(-374.9)] kj = +87.88 kj

here, δh (pcl3) = -287.02 kj, δh(cl2) = 0, δh(pcl5) = -374.9 kj

therefore, enthalpy of the overall reaction is +87.88 kj or +88 kj.