Calculate the heat change associated
with cooling a 350.0 g aluminum bar
from 70.0/C to 25.0/C. Is the change
endothermic or exothermic? Why?
(-14.2 kJ)

Heat change is -14,175 joules, Exothermic

Explanation:

We are given;

We are required to determine the heat change and indicate whether endothermic or exothermic;

We know that;

Heat change = Mass of a substance × specific heat × change in temperature

In this case;

Mass of Aluminium = 350.0 g

Change in temperature = (25 - 70)

                                       = -45° C

Specific heat of aluminium = 0.90 J/g°C

Therefore;

Heat change = 350.0 g × 0.90 J/g°C × -45°C

                     =-14,175 joules

The heat change is exothermic because it is a negative value, also because cooling process involves heat loss and thus an exothermic reaction.

answer is a

explanation:

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.