Step 3: Determine the amount of energy change in the reaction. a) Use the table of enthalpy values (Table A) provided in the Student Worksheet to locate the enthalpy of formation (∆Hf) for each reactant and each product. Record these values along with the reactants and products in Table B of the Student Worksheet. b) Determine the total enthalpy of the reactants and the total enthalpy of the products. Record these values in Table C of the Student Worksheet. c) Use the following formula to find the net change in enthalpy for the reaction and to determine whether the reaction is endothermic or exothermic.

Explanation:

Assume the reaction is the combustion of propane.

Word equation: propane plus oxygen produces carbon dioxide and water

Chemical eqn:    C₃H₈(g) +   O₂(g) ⟶   CO₂(g) +   H₂O(g)

Balanced eqn:    C₃H₈(g) + 5O₂(g) ⟶ 3CO₂(g) + 4H₂O(g)

(a) Table of enthalpies of formation of reactants and products

(b)Total enthalpies of reactants and products

ΔᵣH° is negative, so the reaction is exothermic.

b. atoms in metallic solids are not arranged in a regular pattern

explanation:

the equation that correctly represent the reaction for formation of ammonia is

n2+ 3h2 → 2nh3 (answer d)

1 mole of nitrogen gas (n2) react with 3 moles of hydrogen gas (h2) to form 2 moles of ammonia ( nh3). this is in a process known as haber process were iron is used as a catalyst and reaction take place that a higher temperature and pressure. the process is exothermic hence energy is released.