Ch 2: Energy from Fuels

Question 1

activation energy

Answer 1

the minimum energy required by reactants for a chemical reaction to occur. it is the energy required to break the bonds between the atoms of the reactants to allow products to form.

Question 2

avogadro’s number

Answer 2

the number of particles in one mole of any substance, equivalent to 6.023 x 10^23 particles.

Question 3

bond energy

Answer 3

the energy required to break a covalent bond.

Question 4

bond strength

Answer 4

the strength of a covalent bond. in general, the higher the bond energy the greater the bond strength.

Question 5

chemical energy

Answer 5

the sum of the chemical potential and kinetic energy in a substance. chemical energy is stored in the bonds between atoms and molecules.
the energy results from things such as: attractions between electrons and protons in atoms, repulsion between nuclei, repulsions between electrons, movement of electrons, vibrations and rotations around bonds.

Question 6

combustion reaction

Answer 6

a combustion reaction which takes place with sufficient oxygen. the products of complete combustion of hydrocarbons are co2 and h2o

Question 7

endothermic

Answer 7

a reaction that absorbs energy from the surroundings. delta H is positive.

Question 8

energy profile diagram

Answer 8

a diagram which shows the energy changes during a chemical reaction

Question 9

enthalpy

Answer 9

heat content. the sum of chemical potential and kinetic energies in a substance; symbol H

Question 10

enthalpy change

Answer 10

the difference in the total enthalpy of the products and the total enthalpy of the reactants, symbol delta H. also known as heat of reaction

Question 11

enthalpy of combustion

Answer 11

the enthalpy released when a specified quantity (eg one mole or one gram) of a substance is burned completely in oxygen; symbol delta H

Question 12

exothermic

Answer 12

a reaction which releases energy to the surroundings. delta H is negative

Question 13

heat of combustion

Answer 13

the energy released when a specified quantity (eg 1 mole or 1 gram) of a substance burns completely in oxygen

Question 14

heat of reaction

Answer 14

the difference in enthalpy between the reactants and products during a chemical reaction. also known as enthalpy change

Question 15

incomplete combustion

Answer 15

a combustion process that takes place when oxygen is limited. incomplete combustion of hydrocarbons produces carbon and carbon monoxide as well as carbon dioxide

Question 16

molar mass

Answer 16

the mass of one mole or equivalent of a compound