Chem2 Definitions

Enthaply Change - Heat energy transferred in a reaction at constant pressure.

Standard Enthalpy Change of Formation - Enthalpy change when 1 mole of a compound is formed from it's elements in their standard states under standard comditions.

Standard Enthalpy Change of Combustion - Enthaply change when 1 mole of a substance is burnt completely in oxygen under standard conditions, all products and reactants being in their standard states.

Hess's Law - Total enthalpy change is always the same and is independent of the route taken.

Average Bond Enthalpy - Energy needed to break 1 mole of bonds in the gas phase, averaged over many different compounds.

Activation Energy - Minimum amount of kinetic energy that particles need for a reaction to occur.

Rate of Reaction - Change in concentration in a given time.

Catalysts - Increases rate of reaction by providing an alternative reaction pathway with a lower activation energy. The catalyst remains chemically unchanged at the end of the reaction.

Le Chatelier's Principle - If there's a change in concentration, pressure or temperature, the equilibrium will move to help counteract the change.

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Most collisions do not lead to a reaction.  - Reaction won't take place unless 1) They collide in the right direction. 2) They collide with at least a certain amount of energy. Increase Temperature Small increase in temperature can lead to a big change in rate of reaction. - More kinetic energy - Particles move faster - MANY MORE particles have energy greater than the activation energy and are able to react. Increase Concentration or Pressure - Particles closer together - More chance of a collision. - More chance of effective reaction. Increase Surface Area If in big lump, most particles won't collide with other reactants. Crush lumps; more particles in contact with other reactants. - Smaller particle size. - Larger surface area. - More particles likely to collide - More chance of effective reaction. - Faster rate of reaction. Catalysts - Activation energy lower. - Particles need lower energy to react - More particles have energy greater than the activation energy. - More particels likely to collide - More chance of effective reaction. Investigating Reaction Rates ~Measure... Volume of gas or decrease in mass. ~Time... How long it takes for precipitate to form.

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Reversible Reactions

# As reactants get used up, forward reaction slows down.

# As more product formed, reverse reaction speeds up.

DYNAMIC EQUILIBRIUM: Forward and backward reactions happen at the same rate.

Catalysts don't affect the position of equilibrium. Can't increase the yield - means equilibrium is reached faster.

Concentration - Increase concentration of a reactant, equilibrium tries to get rid of extra reactant. It makes more product. Equilibrium's shifted to the right.

  - Increase concentratation of a product, equilibrium tries to remove extra product. Reverse reaction faster. Equilibrium shifts left.

  - Decreasing concentration has opposite effect.

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Can you just add Carbon Neutral?

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