Thermochemical Equations Project: Modeling Energy Changes Assignment Summary In this assignment, you will write and balance a chemical equation. Then, you will use a table of enthalpy values to calculate the energy change in the reaction. Next, you will create a model of the energy change in the reaction. Finally, you will write an explanation that describes the energy change in the reaction.

Thermochemical Equation

Thermochemistry

Thermochemical Equation

Define thermochemical equation.

Define heat of reaction.

What is the best way to heat a house?

Heating a home is becoming more and more expensive. Do we use gas, oil, electricity, wood? Part of the decision is based on which fuel will provide the highest amount of energy release when burned. Studies of thermochemistry can be very useful in getting reliable information for making these important choices.

a gas furnace

Thermochemical Equation

When methane gas is combusted, heat is released, making the reaction exothermic. Specifically, the combustion of 1 mol of methane releases 890.4 kilojoules of heat energy. This information can be shown as part of the balanced equation.

text{CH}_4(g)+2text{O}_2(g) rightarrow text{CO}_2(g)+2text{H}_2text{O}(l)+890.4 text{kJ}

The equation tells us that 1 mol of methane combines with 2 mol of oxygen to produce 1 mol of carbon dioxide and 2 mol of water. In the process, 890.4 kJ is released and so it is written as a product of the reaction. A thermochemical equation is a chemical equation that includes the enthalpy change of the reaction. The process in the above thermochemical equation can be shown visually in the Figure below .

first let us lay out the formula for potential

and kinetic energy:

pe = mgh

ke = (mv^2)/2

where: m=mass, v=velocity, g=gravitational

acceleration, h=height

calculating for mass using the known values of

pe:

340j = m (9.81 m/s^2) (50ft) (1m/3.28ft)

m = 2.27 kg

the law of conservation of energy states that

energy is neither created nor destroyed. therefore, the change in kinetic

energy from 50 ft to 35 ft would be equal to the change in potential energy

from 50 ft to 35 ft. however it would be opposite in signs since one is losing

while other is gaining.

ke(35ft) – ke(50ft) = - [ pe(35ft) – pe(50ft]

ke(50ft) = 0 since the brick is initially at rest

ke(35ft) = 340j - 2.27kg (9.81 m/s^2) (35ft)

(1m/3.28 ft)

ke(35ft)

= 102.38 j