In Shakespeare's Othello, how does Othello blame Desdemona for doing bad things?

In Shakespeare's Othello, Othello blames Desdemona for supposedly being unfaithful to him by continually calling her a "strumpet," or in other words a whore.  When Othello tells Desdemona that she is on her deathbed, he asks her if she has prayed that evening, which suggests that Othello believes Desdemona to be a sinner--he wants her to make herself right with the Lord before he ends her life.  Othello believes the ruse that Iago has set up throughout the play, and Othello thus refers to the supposed affair with Michael Cassio.  At first, Desdemona is not aware of the reason why Othello has claimed her to be false, but later he tells her directly that she must be murdered for having had an affair with Cassio.  Although Desdemona tells Othello the claim is false, Othello does not believe her and continues blaming her for being unfaithful.