Item EB005003: The reaction between nitrogen and hydrogen gives off energy because the total bond energy of the reactants is less than the total bond energy of the products.
The production of a fertilizer involves the chemical reaction between nitrogen (N2) and hydrogen (H2) to form ammonia (NH3). In the equation for this reaction shown below, blue circles labeled N represent nitrogen atoms and white circles labeled H represent hydrogen atoms. Lines represent bonds between the atoms that make up molecules.
Scientists have determined the amount of energy associated with both breaking and forming the bonds between the atoms that make up the molecules of N2, H2, and NH3. The table below lists the total amount of energy associated with breaking the bonds of the reactant molecules (1 mole of N2 and 3 moles of H2) and the total amount of energy associated with forming the bonds of the product molecules (2 moles of NH3). [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 + 3 H2 | 537 kcal |
Products | 2 NH3 | 837 kcal |
Based on this information, does this reaction give off or take in energy and why?
- The reaction takes in energy because energy is taken in by all chemical reactions regardless of differences in total bond energy.
- The reaction takes in energy because the total bond energy of the reactants is less 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 energy.
- The reaction gives off energy because the total bond energy of the reactants is less than the total bond energy of the products.
- Distribution of Responses
![Chart showing distrubtion of responses for Item EC005003](http://chart.apis.google.com/chart?chs=265x180&cht=bvg&chf=bg,s,00000000&chco=76A4FB|76A4FB|76A4FB|339933&chds=0,100&chd=t:22,28,32,17&chxl=0:|A|B|C|D&chxt=x,y&chbh=a&chbw=a&chm=N*f0*%,000000,0,-1,11,,e::5&filename=EC005003-dist.png)
- Points Earned
Group | Correct | Total | Percent |
---|---|---|---|
Overall | 30 | 174 | 17% |
Grades | |||
6–8 | N/A | N/A | N/A |
9–12 | 26 | 159 | 16% |
Gender | |||
Male | 14 | 88 | 16% |
Female | 12 | 69 | 17% |
Primary Language | |||
English | 27 | 152 | 18% |
Other | 0 | 8 | 0% |
- Distribution of Responses
![Chart showing distrubtion of responses for Item EC005003](http://chart.apis.google.com/chart?chs=265x180&cht=bvg&chf=bg,s,00000000&chco=76A4FB|76A4FB|76A4FB|339933&chds=0,100&chd=t:10,42,12,36&chxl=0:|A|B|C|D&chxt=x,y&chbh=a&chbw=a&chm=N*f0*%,000000,0,-1,11,,e::5&filename=EC005003-dist.png)
- Points Earned
Group | Correct | Total | Percent |
---|---|---|---|
Overall | 64 | 177 | 36% |
Grades | |||
6–8 | N/A | N/A | N/A |
9–12 | 59 | 165 | 36% |
Gender | |||
Male | 36 | 101 | 36% |
Female | 23 | 59 | 39% |
Primary Language | |||
English | 51 | 149 | 34% |
Other | 6 | 13 | 46% |
- 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.