Copyright © Glencoe/McGraw-Hill, a division of The McGraw-Hill Companies, Inc.
Solving Problems: A Chemistry Handbook
Chemistry: Matter and Change
169
Chemical Equilibrium
Chemical Equilibrium
SOLVING PROBLEMS:
A CHEMISTRY HANDBOOK
CHAPTER
17
17.1 Equilibrium: A State of Dynamic Balance
A reversible reaction is a reaction that can take place in both the
forward and reverse directions. An example is the reaction of hydrogen and bromine at elevated temperature to form hydrogen bromide,
and the reverse reaction, the decomposition of hydrogen bromide
into its elements.
H 2 (g) ϩ Br 2 (g) 0 2HBr(g)
2HBr(g) 0 H 2 (g) ϩ Br 2 (g)
These two equations may be combined into a single equation with a
double arrow to show that both reactions occur.
H 2 (g) ϩ Br 2 (g) 3 2HBr(g)
When forward and reverse reactions occur at equal rates, a state of
chemical equilibrium results in which the concentrations of reactants and products remain constant.
The law of chemical equilibrium states that at a given temperature, a chemical system may achieve a state in which a certain ratio
of reactant and product concentrations has a constant value. The
general equation for a reaction at equilibrium is as follows.
aA ϩ bB 3 cC ϩ dD
The law of chemical equilibrium may be used to write the equilibrium constant expression for the reaction.
K eq ϭ
The equilibrium constant, K eq , is the value of the ratio of the molar
concentrations of the products divided by the molar concentrations
of the reactants, with each concentration raised to the power equal to
its coefficient in the balanced equation. For example, consider the
reversible formation of hydrogen bromide.
H 2 (g) ϩ Br 2 (g) 3 2HBr(g)
[C] c [D] d
ᎏ
[A] a [B] b
Solving Problems: A Chemistry Handbook
Chemistry: Matter and Change
169
Chemical Equilibrium
Chemical Equilibrium
SOLVING PROBLEMS:
A CHEMISTRY HANDBOOK
CHAPTER
17
17.1 Equilibrium: A State of Dynamic Balance
A reversible reaction is a reaction that can take place in both the
forward and reverse directions. An example is the reaction of hydrogen and bromine at elevated temperature to form hydrogen bromide,
and the reverse reaction, the decomposition of hydrogen bromide
into its elements.
H 2 (g) ϩ Br 2 (g) 0 2HBr(g)
2HBr(g) 0 H 2 (g) ϩ Br 2 (g)
These two equations may be combined into a single equation with a
double arrow to show that both reactions occur.
H 2 (g) ϩ Br 2 (g) 3 2HBr(g)
When forward and reverse reactions occur at equal rates, a state of
chemical equilibrium results in which the concentrations of reactants and products remain constant.
The law of chemical equilibrium states that at a given temperature, a chemical system may achieve a state in which a certain ratio
of reactant and product concentrations has a constant value. The
general equation for a reaction at equilibrium is as follows.
aA ϩ bB 3 cC ϩ dD
The law of chemical equilibrium may be used to write the equilibrium constant expression for the reaction.
K eq ϭ
The equilibrium constant, K eq , is the value of the ratio of the molar
concentrations of the products divided by the molar concentrations
of the reactants, with each concentration raised to the power equal to
its coefficient in the balanced equation. For example, consider the
reversible formation of hydrogen bromide.
H 2 (g) ϩ Br 2 (g) 3 2HBr(g)
[C] c [D] d
ᎏ
[A] a [B] b