The electrical properties of a (5,0) zigzag single-walled carbon nanotube (SWCNT) functionalized with gold and its potential for acetone sensing are investigated in this study utilizing density functional theory (DFT) calculations. We choose the well-known Perdew-Burke-Ernzerhof (PBE) functional due to its accuracy and computational effectiveness. The choice of exchange-correlation function is crucial in DFT calculations. We perform both band structure and density of states (DOS) calculations using Visualization of Electronic and STructural Analysis (VESTA) and Quantum ESPRESSO (QE). We observe the band gap for CNT, Au-CNT, C3H6O-CNT, and Au-CNT-C3H6O are 0eV, 0.54eV, 1.12eV, and 0.35eV. Our research enhances knowledge of functionalized carbon nanotubes for use in gas sensing applications and emphasizes the use of the PBE functional, as well as the software suites VESTA and QE.