An automated chemical analyzer measures the pH levels of seven sequential samples from an industrial discharge pipe, storing them in a one-dimensional array:
| 5.8 | 4.2 | 6.1 | 3.9 | 7.4 | 5.1 | 6.8 |
Explain why a binary search algorithm cannot be used to find a sample with a pH of 5.1 in this array.