To calculate the percent error, we can use the following formula:
```
percent error = (|experimental value - expected value| / expected value) * 100%
```
In this case, the experimental value is 154.8 g and the expected value is 171.9 g. Plugging these values into the formula, we get:
```
percent error = (|154.8 g - 171.9 g| / 171.9 g) * 100%
```
```
percent error = (17.1 g / 171.9 g) * 100%
```
```
percent error = 9.95%
```
Therefore, the percent error for this experiment is 9.95%.