What is the irony contained in the short story, "The Story of an Hour" by Kate Chopin?

In Chopin's "The Story of an Hour," the woman is expected
to feel badly about her husband's death.  The other characters are worried that her
heart trouble could cause a problem because she is shocked and hurt by her husband's
death.  And they worry about her becoming too distraught when she is by herself in her
room.

In actuality, the opposite of all of the above
happens.  That's irony. 

Her initial reaction to the death
of her husband is what's expected, but not for long.  Instead, she feels a release, a
sense of freedom.  Her subservience to her husband is over, and she rejoices.  Her heart
causes her trouble when she finds out her husband is still alive, not when she hears
that he is dead.  And she is anything but distraught.  During her time alone in her
room, she discovers a sense of freedom she, apparently, has not felt for a long
time. 

Chopin uses plot, character thoughts and dialogue,
imagery, and symbolism to construct the story and reveal its
irony.