The Gift:
After Macbeth's successful usurpation of the throne, he becomes increasingly paranoid and guilt-ridden. To appease his wife and strengthen their position, Macbeth decides to bestow upon her a grand and luxurious gift. He announces that he plans to give her the title of "Queen of Scotland" and grant her authority and power equal to his own.
The Dramatic Irony:
The dramatic irony in this situation arises from the audience's knowledge of the true state of Macbeth and Lady Macbeth. While Macbeth believes he is giving his wife a valuable and desirable gift, the audience is aware that this title is tainted by the blood of King Duncan and the guilt that consumes Macbeth.
The gift of the "Queen of Scotland" title highlights the contrast between Macbeth's perception of the crown as a symbol of glory and power and the audience's understanding that it is a burden of guilt and remorse. The disparity between Macbeth's intentions and the reality known to the audience creates a sense of dramatic irony.