A few examples of what you can ask Wolfram|Alpha about:
get information about a chemical element
compare several elements
do computations using properties of chemical elements
get information about a chemical compound
compare properties of multiple compounds
analyze properties of a class of compounds
get information about an ion
compare several ions
get information about a class of ions
compute properties of a quantity of a chemical
compute properties of a chemical solution
compute properties of a quantity of a solution
find properties of a substance in a given phase
compute properties at a specified temperature
Functional Groups
get information about a functional group
get information about a protecting group
find behavior under specified conditions
Chemical Formulas
find isomers with a given formula
get a formula for a chemical
3D Structures
see the three-dimensional structure of a molecule
compute topological properties of a molecule
pH Indicators
find the indicators for a particular pH
Orbital Hybridization
compute hybridization in a compound
compare hybridization in two compounds