MEGA
Energy Changes
Some chemical reactions release energy into the surroundings, whereas other chemical reactions take in energy fr…
Item EC006003: A scientist can use the energy from burning 1 mole of carbon (from coal) to provide the energy needed to make one mole of CaO because the reaction of one mole of C with O2 will give off more energy than is needed to produce one mole of CaO.
A scientist wants to produce calcium oxide (CaO) and carbon dioxide (CO2) from calcium carbonate (CaCO3), as represented by the following equation.
CaCO3 → CaO + CO2
He estimates that this reaction requires a net input of 43 kcal of energy for every mole of CaO produced. [A kilocalorie (kcal) is a unit of energy and a mole is a very large quantity of molecules.]
The scientist wants to know if the burning of coal can provide the needed energy for this reaction. He determines that when the carbon (C) in coal reacts with oxygen (O2) according to the equation below, 94 kcal of energy is given off to the surroundings for every mole of carbon burned.
C + O2 → CO2
Could the scientist use the energy from burning 1 mole of carbon (from coal) to provide the energy needed to make one mole of CaO?
- Yes, because both reactions form one mole of carbon dioxide (CO2).
- Yes, because the reaction of one mole of C with O2 will give off more energy than is needed to produce one mole of CaO.
- No, because the product of burning one mole of carbon is not the same as the reactant of the CaCO3 reaction.
- No, because energy given off by one reaction cannot supply the energy needed by another reaction.
Pre-Test
Answer Choice |
Overall |
Grades |
Gender |
Primary Language |
||||
|---|---|---|---|---|---|---|---|---|
| n = 160 |
6–8 n = 0 |
9–12 n = 138 |
Male n = 81 |
Female n = 60 |
English n = 127 |
Other n = 7 |
||
| A. | Yes, because both reactions form one mole of carbon dioxide (CO2). | 20% | NAN% | 20% | 20% | 18% | 20% | 14% |
| B. | Yes, because the reaction of one mole of C with O2 will give off more energy than is needed to produce one mole of CaO. | 31% | NAN% | 33% | 36% | 30% | 33% | 14% |
| C. | No, because the product of burning one mole of carbon is not the same as the reactant of the CaCO3 reaction. | 31% | NAN% | 30% | 31% | 28% | 28% | 71% |
| D. | No, because energy given off by one reaction cannot supply the energy needed by another reaction. | 18% | NAN% | 17% | 14% | 23% | 19% | 0% |
Post-Test
Answer Choice |
Overall |
Grades |
Gender |
Primary Language |
||||
|---|---|---|---|---|---|---|---|---|
| n = 171 |
6–8 n = 0 |
9–12 n = 159 |
Male n = 87 |
Female n = 70 |
English n = 146 |
Other n = 11 |
||
| A. | Yes, because both reactions form one mole of carbon dioxide (CO2). | 15% | NAN% | 14% | 13% | 17% | 15% | 9% |
| B. | Yes, because the reaction of one mole of C with O2 will give off more energy than is needed to produce one mole of CaO. | 49% | NAN% | 51% | 55% | 43% | 51% | 55% |
| C. | No, because the product of burning one mole of carbon is not the same as the reactant of the CaCO3 reaction. | 27% | NAN% | 25% | 22% | 30% | 23% | 36% |
| D. | No, because energy given off by one reaction cannot supply the energy needed by another reaction. | 9% | NAN% | 10% | 10% | 10% | 11% | 0% |