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12 Cards in this Set
- Front
- Back
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What are the units of Enthalpy? |
Kilojoules per mole kJmol⁻¹ |
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What is meant by the word "system"? |
-The reactants and products -can lose or gain energy |
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What is meant by the word "surroundings"? |
The rest of the world, i.e. the test tube, air |
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Define ∆Hcº |
The enthalpy change that occurs when one mole of a substance completely burns in excess oxygen under standard conditions. |
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State Hess' Law |
The enthalpy change for ay substance is independent of the intermediate stages, so long as the initial and final conditions are the same for each route. |
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Define endothermic reaction, including energy change diagram |
Enthalpy of reacting system increases, takes in energy from surroundings. |
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Define ∆Hrº |
The enthalpy change when molar quantities of reactants as stated in the equation react together under standard conditions. All the substances are in their standard states. |
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What are the standard conditions? (with units) |
-Specified temperature --> 298ºK -Standard pressure of 1 atomsphere --> 1.01x10⁵ N m⁻² -Standard concentration of 1 mold dm⁻³ |
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Define exothermic reaction, including energy change digram. |
Enthalpy of reacting system decreases, gives out het and energy to the surroundings. |
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Define ∆Hfº |
The standard enthalpy change one mole of a compound is formed from its constituent elements, with both the compound and elements in their standard states. |
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Symbol for enthalpy and its definition. |
∆H The measure of energy transferred to and from the surroundings. |
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What equation do we use to work out the energy transferred? |
-∆H = products - Hreactants -q= mc∆T -q= energy transferred -m= mass of substance being heated by the fuel -c= speciific heat capacity (4.18 for water) -∆T= change in temperature of substance being heated. |
