In Kate Chopin's short story "The Story of an Hour", Louise Mallard's actual mood and her sister Mrs. James's perception of it create an ironic situation.
Mrs. James believes Louise to be heartbroken over the presumed death of her husband, Mr. Mallard. She thinks Louise is in a state of deep sorrow and mourning. However, Louise's real mood is quite the opposite. She feels a sense of freedom and joy upon realizing she will now be independent and unchained to her oppressive marriage.
This creates irony of situation. Mrs. James misreads Louise's emotions entirely, thinking her to be devastated when she is quite delighted. The irony lies in the mismatch between the perception of Louise's mood and its reality.
There is also irony of dramatic reversal. The happiness Louise begins to experience is suddenly and tragically cut short by the reappearance of her supposedly dead husband. The freedom she tasted is abruptly snatched away, and she dies of shock upon seeing him.
So the story reflects both irony of situation/misperception as well as irony of reversal or twists of fate. The situations are ironic replications of expectations versus realities. And there is a tragic twist of events undermining the joy that seemed Louise's for the taking. All of these create the poignant and unsettling effect of the story's irony.
Does this help explain the irony and mood contrasts in the story? Let me know if you need any clarification or have additional questions!