An example of situational irony in "The Story of an Hour" is when Louise Mallard discovers that her husband, Brently Mallard, is still alive. The fact that Mrs. Mallard dies of heart failure after learning that her husband is still alive is also an example of situational irony.
Situational irony is described as an unexpected twist in a story that differs from what the reader anticipated. "The Story of an Hour" describes the emotions of a woman who has recently heard the news of the death of her husband. Before it is revealed that Mr. Mallard is in fact alive, the reader is so immersed in the different emotions that Mrs. Mallard is feeling that the news of him being alive is unforeseen.