The word "bang" appears nineteen times in the text, and not in any sort of context like a sentence, either. Instead, they're little interjections, words that erupt into the text when something important happens. So let's look at exactly where they show up:
The first "bang" appears when Macabéa's boss, Senhor Raimundo Silveira, warns her that she will probably soon be fired because he is tired of her typing mistakes. So, what we're getting here is that "bang" occurs after some disturbing (and probably surprising) news.
The second "bang" appears when the narrator announces to us that he is about to tell us Macabéa's history (3.60). This is a little different, but it still signals a shift of some sort. It tells us that something has changed.
And how check out the section in which they appear the most. Nine of the nineteen "bangs" appear in when Macabéa visits Madame Carlota, the fortuneteller. Here's a list of those "bang" moments in Chapter 5:
- When Macabéa is convinced that Madame Carlota is about to reveal her destiny: "Macabéa divided the pack [of cards] with a trembling had: for the first time in her life, she was about to know her destiny. Madame Carlota (bang) was to be the climax of her existence" (5.393).
- When Madame Carlota's face lights up because she's about to give Macabéa good news about her future (after telling her how horrible her life has been): "Whereupon (bang) something happened out of the blue: Madame Carlota's face suddenly lit up: 'Macabéa! I have some wonderful news for you!'" (5.399-400).
- When Macabéa feels the urge to start living for the future: "Macabéa's eyes opened wide as she felt a sudden hunger for the future (bang)" (5.400).
- When Madame Carlota tells Macabéa about a foreigner named Hans whom she will marry: "No! No! No! I can see something else (bang) and though I cannot see it very clearly, I can also hear the voice of my guiding spirit: this foreigner is apparently called Hans, and he is the man whom you will marry!" (5.403).
- When Macabéa starts physically shaking from excessive happiness: "Macabéa began (bang) to tremble all over, for there is a painful side to a surfeit of happiness" (5.404).
So, whenever "big" news is about to be announced or when Macabéa has a strong and new emotion or reaction, we get a "bang." They signal a change and a shift; we get the sense that Macabéa is one person before a "bang" and a different person after the "bang."
Oh yeah, and the final "bang"? Right before the yellow Mercedes runs her over.