MEGA
Energy Changes
Chemical energy is associated with the arrangement of atoms that make up the molecules of the reactants and prod…
Item EB004005: The reaction between nitrogen and oxygen takes in energy because the total bond energy of the reactants is greater than the total bond energy of the products.
Nitrogen (N2) can react with oxygen (O2) to form nitric oxide (NO) as shown in the following reaction equation.
N2 + O2 → 2 NO
Scientists have determined the amount of energy associated with breaking and forming the bonds between the atoms that make up the molecules of N2, O2, and NO. The table below lists the total amount of energy associated with breaking the bonds of the reactant molecules (1 mole of N2 and 1 mole of O2) and the total amount of energy associated with forming the bonds of the product molecules (2 moles of NO). [A kilocalorie (kcal) is a unit of energy and a mole is a very large quantity of molecules.]
| Total bond energies in kilocalories (kcal) | ||
| Reactants | N2 + O2 | 344 kcal |
| Products | 2 NO | 302 kcal |
Based on this information, does this reaction give off or take in energy and why?
- The reaction gives off energy because the total bond energy of the reactants is greater than the total bond energy of the products.
- The reaction gives off energy because energy is given off by all chemical reactions regardless of differences in total bond energies.
- The reaction takes in energy because the total bond energy of the reactants is greater than the total bond energy of the products.
- The reaction takes in energy because energy is taken in by all chemical reactions regardless of differences in total bond energies.
- Distribution of Responses
- Points Earned
| Group | Correct | Total | Percent |
|---|---|---|---|
| Overall | 52 | 164 | 32% |
| Grades | |||
| 6–8 | N/A | N/A | N/A |
| 9–12 | 44 | 141 | 31% |
| Gender | |||
| Male | 22 | 82 | 27% |
| Female | 23 | 63 | 37% |
| Primary Language | |||
| English | 42 | 129 | 33% |
| Other | 1 | 8 | 13% |
- Distribution of Responses
- Points Earned
| Group | Correct | Total | Percent |
|---|---|---|---|
| Overall | 59 | 171 | 35% |
| Grades | |||
| 6–8 | N/A | N/A | N/A |
| 9–12 | 55 | 158 | 35% |
| Gender | |||
| Male | 25 | 87 | 29% |
| Female | 28 | 69 | 41% |
| Primary Language | |||
| English | 51 | 145 | 35% |
| Other | 4 | 11 | 36% |
- Disciplinary Core Ideas
- PS1.A A stable molecule has less energy than the same set of atoms separated; one must provide at least this energy in order to take the molecule apart.
PS1.B Chemical processes, their rates, and whether or not energy is stored or released can be understood in terms of the collisions of molecules and the rearrangements of atoms into new molecules, with consequent changes in the sum of all bond energies in the set of molecules that are matched by changes in kinetic energy.