# Chemistry Developing fuels

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• Created by: Chloesn
• Created on: 03-01-14 20:05
Using equations to work out reacting masses Step 1 and 2 (1.3)
A balanced equation tells you the amount in moles of each substance involved in the reaction. Step 1 Write a balanced equation. SStep 2 In words, state what the equations tells you about the amount in moles of the substance your interested in.
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Using equations to work out reacting masses Step 3 and 4 (1.3)
Step 3 Change the amounts in moles into masses. Step 4 Scale the masses to the ones in the question.
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Gas molecules are very far apart so size of each is unimportant in the effect on volume occupied. So 1 mole of gas occupies? (1.4)
1 mole of gas always occupies the same volume
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Gas and standard and room conditions? (1.4)
Standard (S.T.P) 22dm3 Temp 0oC (273K) Pressure of 1 atmosphere (101.3kPa) At room temperature (R.T.P) 24dm3 Temp 25oC (298K) Pressure of 1 atmosphere
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Exothermic? (4.1)
Many chemical reactions give out energy - exothermic. Gives out energy Heats surroundings
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Endothermic? (4.1)
Few chemical reactions take in energy - endothermic. Takes in energy Cools surroundings
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We measure the energy transferred as ENTHALPY CHANGE. (4.1)
In an exothermic reaction the reactants are losing energy so the products end up with less energy than the products and the surroundings ends up with more.
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For an exothermic reaction ΔH is negative. Why? (4.1)
From this view chemical reactants, energy is lost to the surroundings.
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For an endothermic reaction ΔH is positive. Why? (4.1)
Energy has been gained from the surroundings.
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Like most, ΔH also varies according to the conditions. In particular, temp,pressure and concentration of solutions, so we choose standard conditions: (4.1)
a specified temperature a standard pressure of 1 atmosphere (1.01 x 105 Nm-2) a standard concentration of 1 mol dm-3
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Measuring the temperature of the water and knowing its mass and specific heat capacity, we can work out how much energy was transferred to/from the water. (4.1)
If it’s exo the water gets hotter; if it’s endo the water gets cooler.
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The relationship for this - (4.1)
Energy transferred = cm ΔT c is the specific heat capacity of water (4.18Jg-1K-1) m is the mass of water in g The relationship for this - ΔT is the change in temperature of the water
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## Other cards in this set

### Card 2

#### Front

Using equations to work out reacting masses Step 3 and 4 (1.3)

#### Back

Step 3 Change the amounts in moles into masses. Step 4 Scale the masses to the ones in the question.

### Card 3

#### Front

Gas molecules are very far apart so size of each is unimportant in the effect on volume occupied. So 1 mole of gas occupies? (1.4)

### Card 4

#### Front

Gas and standard and room conditions? (1.4)

### Card 5

#### Front

Exothermic? (4.1)