Energetics

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  • Created by: elyornais
  • Created on: 20-02-15 23:32
What is thermochemistry?
The study of heat changes in a chemical reaction.
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What does breaking bonds require?
Energy.
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What happens when bonds are made?
Energy is released.
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What is enthalpy change?
Heat energy change measured under conditions of constant pressure.
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What is meant by standard enthalpy change?
Under standard conditions(100KPa and 298k) and states of elements.
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How would you calculate the enthalpy change from the heat change in a reaction?
q= m*c* deltaT
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What is the definition of the standard enthalpy of formation?
The energy change when 1 mole of a substance is formed from it's constituent elements under standard conditions, all reactants and products in their standard states.
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What is the definition of the standard enthalpy of combustion?
The energy change when 1 mole of a substance is burned completely in oxygen under standard conditions, all reactants and products in their standard states.
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How do we know if a reaction is exothermic?
The products have less heat energy than reactants because they lose heat and the enthalpy change is negative.
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How do we know if a reaction is endothermic?
The products have more heat energy than the reactants as they take heat from the surroundings and the enthalpy change is positive.
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What does temperature mean?
The AVERAGE kinetic energy of particles in a system and is independet of number of particles present.
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What is meant by heat?
The TOTAL energy of all particles present in a given amount of substances. Energy of every particle is included.
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What are the steps to calculating enthalpy change?
1.Write full equation. 2.Work out temp change 3.q=MC TempChange 4.Work out for 1 mole. 5.Make it negative because heat is given out.
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What is equation for an acid being neautralised by an alkali?
Acid+ alkali -> salt + water
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What kind of reaction is a neutralisation reaction?
Exothermic.
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How to work out enthalpy change in a solution?
1.Work out enthalpy change. 2.Work out the number of moles (M*V/1000) 3.Divide enthalpy change by moles. 4.Divide by 1000 to convert to KJ/mol 5.Change to negative because it is exothermic.
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State Hess' Law.
The enthalpy change for a chemical reaction is the same,whatever route is taken from reactants to products.
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What is the enthalpy of all elements in their standard states?
zero
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Other cards in this set

Card 2

Front

What does breaking bonds require?

Back

Energy.

Card 3

Front

What happens when bonds are made?

Back

Preview of the front of card 3

Card 4

Front

What is enthalpy change?

Back

Preview of the front of card 4

Card 5

Front

What is meant by standard enthalpy change?

Back

Preview of the front of card 5
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