Chemistry: Chemical Equilibria
This flashcard set explains how reversible reactions are represented and the conditions required for equilibrium to be established. It highlights that equilibrium can be approached from either direction and describes the dynamic balance achieved between reactants and products in a closed system.
how is it often denoted that a reaction is reversible
using a double headed arrow
Key Terms
how is it often denoted that a reaction is reversible
using a double headed arrow
where can an equilibrium only be established
in a closed system
where can equilibrium be set up from
either direction
what is reached at equilibrium
a natural balance between products and reactants
why are chemical equilibria dynamic
both the forward and reverse reactions continue to occur
rate of forward reaction equals…
rate of reverse reaction
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| Term | Definition |
|---|---|
how is it often denoted that a reaction is reversible | using a double headed arrow |
where can an equilibrium only be established | in a closed system |
where can equilibrium be set up from | either direction |
what is reached at equilibrium | a natural balance between products and reactants |
why are chemical equilibria dynamic | both the forward and reverse reactions continue to occur |
rate of forward reaction equals… | rate of reverse reaction |
the concentrations of reactants and products remain constant unless… | the conditions are changed |
| the position of the equilibrium |
le chateliers principle | if a system in equilibrium is subjected to change, the position of the equilibrium will move in the direction which opposes that change |
when will the equilibrium shift to the right | if the conc of reactant is increased/conc of product decreased |
when will the equilibrium shift to the left | if the conc of reactant in decreased/conc of product increased |
which side does the equilibrium shift to if the total pressure is increased | to the side with fewer moles of gas because fewer moles of gas exert less pressure |
which side does the equilibrium shift to if the total pressure is decreased | to the side with more moles of gas because more moles of gas exert more pressure |
what effect does an increase in pressure have on the rate of reaction | increases rate of reaction |
why does increased pressure increase rate of reaction | collisions between molecules are more frequent |
which direction will the equilibrium move in if the temp is increased | the direction of the endothermic reaction (TAKES HEAT IN) |
which direction will the equilibrium move in if the temperature is decreased | the direction of the exothermic reaction (GIVES OUT HEAT) |
what does the way the equilibrium responds to change in temperature depend on | whether the forward reaction is exothermic or endothermic |
what does an increase in temperature always increase | the rate of the forward and backward reactions but to different extents |
what does a catalyst increase the rate of the forward and backward reactions by | the same amount |
what effect does a catalyst have on the equilibrium position/yield | none |
what does using a catalyst increase | the rate at which the equilibrium position is reached |
the haber process | N2(g)+3H2(g)> 2NH3 (g) |
what is dependent on the conditions used in the haber process | the equilibrium position, yield of ammonia and rate of reaction |
what are used in order to balance yield of ammonia, rate of ammonia production and energy requirements | a compromise temperature and pressure |
what pressure is the haber process conducted under | 200 atm |
what temperature is the haber process conducted under | 400-450 degrees celcius |
what catalyst is used in the haber process | iron |
what is also used in the haber process | recycling |
what is Kc | the equilibrium constant in terms of the concentrations of the reactants and products |
Kc= | aA + bB >< cC + dD (C)c(D)d- PRODUCTS/(A)a(B)b- REACTANTS |
what are (A) (B) (C) (D) | the concentrations of the reactants and products at equilibrium |
what are a b c and d | the stoichiometric coefficients of the balanced equation (moles) |
what does the value of Kc indicate | the extent of the reaction |
what does it mean if Kc is less than one | there are more reactants than products, equilibrium lies to left hand side |
what does it mean if Kc is equal to one | reactants = products |
what does it mean if Kc is greater than one | there are more products than reactants so the equilibrium lies to the left hand side |
what do the units for Kc depend on | the reaction, must be determined for each Kc expression |
does the presence of a catalyst or change in concentration affect Kc | no |
what does affect Kc | change in temperature |
what will happen to Kc if the temperature change causes the equilibrium to shift right | Kc will increase |
what will happen to Kc if temperature change causes equilibrium to shift left | Kc will decrease |
what will there be a mixture of when a reversible reaction has reached equilibrium | reactants and products |
what can the amount of each chemical present at equilibrium be determined by | the balanced equation and the initial moles |