How many Carbon - Hydrogen bonds are in each molecule of methane?
If there are 1652 kJ of bond energy in methane, how much energy is there in A single Carbon - Hydrogen bond?
If there is more bond energy in the reactants than the products of a reaction, that reaction is (exothermic / endothermic)
If there is less bond energy in the reactants than the products of a reaction, that reaction is (exothermic / endothermic)
There are about 800 kJ/ mol of energy in the C=0 bond in carbon dioxide
There are about 500 kJ/ mol of energy in the 0=0 bond in oxygen gas
When carbon and oxygen react
kJ of
energy are (released / absorbed)
So that that reaction is (exothermic / endothermic)
What is an open system and a closed system and how are they different?
In the figure to the right which represents the energy in the
chemical bonds in a pile of firewood, mark these 5 points:
1. A pile of cold (low energy) ashes
2. A neatly stacked pile of wood
3. A roaring fire
4. Burning kindling begins to add energy to the pile
5. A pile of hot (but cooling) coals
What is activation energy? How does a catalyst affect activation energy?
Each molecule of methane has 4 Carbon-Hydrogen bonds.
To find the energy in a single Carbon-Hydrogen bond in methane, we divide the total bond energy by the number of Carbon-Hydrogen bonds. Therefore, the energy in a single Carbon-Hydrogen bond in methane would be 1652 kJ / 4 bonds = 413 kJ.
If there is more bond energy in the reactants than the products of a reaction, then the reaction is endothermic.
If there is less bond energy in the reactants than the products of a reaction, then the reaction is exothermic.
When carbon and oxygen react, 800 kJ of energy are released.
Therefore, the reaction is exothermic.
An open system is one that can exchange matter and energy with its surroundings. A closed system is one that can only exchange energy with its surroundings, not matter.
In the figure:
1. A pile of cold (low energy) ashes - Point 1
2. A neatly stacked pile of wood - Point 2
3. A roaring fire - Point 3
4. Burning kindling begins to add energy to the pile - Point 4
5. A pile of hot (but cooling) coals - Point 5
Activation energy is the minimum amount of energy required for a chemical reaction to occur. A catalyst lowers the activation energy of a reaction, making it easier for the reaction to happen. A catalyst does not affect the overall energy change of a reaction, only the energy required to start the reaction.