Final answer:
Petroleum ether is added in labs to extract impurities from substances. The quantity of petroleum ether added can vary and it can be added using a beaker or a separating funnel. The correct option is (b).
Step-by-step explanation:
Petroleum ether is commonly used in labs to extract impurities from substances. When added to a solution, it helps to separate the impurities from the desired substance, allowing for easier purification.
The quantity of petroleum ether added can vary depending on the specific experiment or procedure, but it is typically measured in milliliters.
To add petroleum ether, a beaker or a separating funnel can be used. Both of these containers are suitable for holding liquids and allow for easy addition of petroleum ether to the solution.