To clean your crucible and cover, you are asked to place it in a solution of 6 M nitric acid. You place your crucible in the designated beaker of nitric acid located in the hood. How will you know when it is clean?(select one)
1. When 5-10 minutes have passed and signs of a vigorous reaction have stopped.
2. When 3 minutes have passed.
3. When the formation of bubbles stops.