Phase equilibrium-The state of balance between
2 opposing phases (dissolving and crystallization). This occurs when
a solution is saturated.
REGENTS NOTE***These processes
occur at the SAME RATES. The Concentration remains constant.
Notice after equilibrium is established, the crystallization and
dissolving rates equalize. This is called a DYNAMIC EQUILIBRIUM.
This implies that there is constant change in the particles but
overall the concentration and the mass of the solid remains
constant.
Chemical Equilibrium-The state of balance
between 2 opposing reactions. Once equilibrium is established the
Concentrations Remain CONSTANT
and the
Rates are EQUAL. "CON CON
REqual"
Walking on an escalator example....you are moving but still in the same
place because of an opposing force or reaction in chemistry.
Regents Questions-
Just remember-->"CON CON
REqual"
Saturated is at equilibrium
Jan 2007-43 Which balanced equation represents a phase equilibrium?
(1) H2(g)+ I2(g)<==>
2HI(g) (2) 2NO2(g)<==>
N2O4(g) (3) Cl2(g)<==>
Cl2(l) (4) 3O2(g)<==> 2O3(g)
June 2004-20
Which statement about a system at equilibrium is true?
(1) The forward reaction rate is less than the reverse reaction rate.
(2) The forward reaction rate is greater than the reverse reaction rate.
(3) The forward reaction rate is equal to the reverse reaction rate.
(4) The forward reaction rate stops and the reverse reaction rate
continues.
Aug 2006-19
A chemical reaction is at equilibrium. Compared to the rate of the
forward reaction, the rate of the reverse reaction is (1) faster and
more reactant is produced (2) faster and more product is produced
(3) the same and the reaction has stopped (4) the same and the
reaction continues in both directions
Aug 2002-13
Which statement correctly describes a chemical reaction at equilibrium?
(1) The concentrations of the products and reactants are equal. (2)
The concentrations of the products and reactants are constant. (3)
The rate of the forward reaction is less than the rate of the reverse
reaction. (4) The rate of the forward reaction is greater than the
rate of the reverse reaction.
Jan 2004-17
Given the reaction at equilibrium: H2(g)+
Br2(g)--> 2 HBr(g)
The rate of the forward reaction is (1) greater than the rate of the
reverse reaction (2) less than the rate of the reverse reaction
(3) equal to the rate of the reverse reaction (4) independent of the
rate of the reverse reaction
June 2005-18
Which statement must be true about a chemical system at equilibrium?
(1) The forward and reverse reactions stop. (2) The concentration of
reactants and products are equal. (3) The rate of the forward
reaction is equal to the rate of the reverse reaction. (4) The number
of moles of reactants is equal to the number of moles of product.
Jan 2010-30
Which quantities must be equal for a chemical reaction at equilibrium?
(1) the activation energies of the forward and reverse reactions (2)
the rates of the forward and reverse reactions (3) the concentrations
of the reactants and products (4) the potential energies of the
reactants and products
June 2010-20 Given the equation representing a phase change at
equilibrium: H2O(s)<==>H2O(l)
Which statement describes this equilibrium? (1) The H2O(s)melts
faster than the H2O(l)freezes.
(2) The H2O(l)freezes
faster than the H2O(s)melts.
(3) The mass of H2O(s)must
equal the mass of H2O(l). (4) The mass of H2O(l)and
the mass of H2O(s)each
remain constant.
