An analyst monitors the progress of a reaction between solid magnesium carbonate (MgCO3MgCO_3MgCO3) and excess dilute nitric acid (HNO3HNO_3HNO3) inside an unstoppered Erlenmeyer flask placed on a high-precision digital balance.
The mass of the flask and its contents was recorded at regular intervals. The results are shown in the table and graph below:
| Time (seconds) | Mass of flask and contents (g) |
|---|---|
| 0 | 180.00 |
| 20 | 179.35 |
| 40 | 178.90 |
| 60 | 178.60 |
| 80 | 178.45 |
| 100 | 178.40 |
| 120 | 178.40 |
Explain why there is a decrease in the mass of the flask and contents.
