# C3 Energy Calculations

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• Created by: KAustria
• Created on: 03-05-14 20:51
When food and oxygen react together what time of reaction is it?
exothermic
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What is an alternative way of measuring energy?
Calories, Cal
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What apparatus can we use to measure the amount of energy released when substances are burned?
Calorimeter
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What is the equation used to measure the amount of energy transferred to water in a calorimeter?
Q = m x c x DeltaT (Amount of energy transferred = mass in grams x specific heat capacity 4.2J/g° x change in temperature
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What are the problems with simple calorimeters?
Results are not accurate because much of the energy is released to heat the surroundings.
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How do you compare energy released by burning different substances?
Comparing energy change in kJ per gram or energy change in kJ per mole
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How do you find out energy change in kJ/ mol?
Multiply the energy change by the relative formula mass of the substance
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When measuring the energy transfer in solutions we assume it behaves like water what does this mean in terms of the mass and specific heat capacity?
The mass of the solution is 1cm3 = 1 g and the specific heat capacity is 4.2J/g°
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When a solid is added to a solution of aqueous solution what happens to the volume of this?
It remains the same
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Breaking bonds is what kind of reaction?
Endothermic
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When new bonds are formed what kind of reaction is this?
Exothermic
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What do catalysts do in a reaction?
Provide a different pathway with an activation energy that is lower.
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What is the energy change in exothermic reactions?
Negative
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What is the general bond making and breaking rule for exothermic reactions?
In exothermic reactions, more energy is released than is needed to break existing bonds
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What is the general bind making and breaking rule for endothermic reactions?
In endothermic reactions, more energy is needed to break existing bonds than energy released when making bonds
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What is the energy needed to break the bond between two atoms ?
Bond energy
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How do you calculate the bond energies?
1. Calculate the total amount of energy needed to break all of the bonds in the reactant 2. Calculate the total amount of energy released by the products 3. Calculate the difference
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What new gas is an alternative to fossil fuels?
Hydrogen
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What are the advantages of using hydrogen as a fuel?
Burns easily, Releases a large amount of energy per gram, It only produces water when burnt.
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What are the disadvantages of using hydrogen as a fuel?
1. Need a platinum catalyst which is expensive and easily contaminated. 2. Must be liquified and compressed 3. Safety 4. Storage 5. Supply
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## Other cards in this set

### Card 2

#### Front

What is an alternative way of measuring energy?

Calories, Cal

### Card 3

#### Front

What apparatus can we use to measure the amount of energy released when substances are burned?

### Card 4

#### Front

What is the equation used to measure the amount of energy transferred to water in a calorimeter?

### Card 5

#### Front

What are the problems with simple calorimeters?