# What is the mass of the rubber stopper in the flask?

## Calculation of the Mass of the Rubber Stopper:

**Step 1:** Determine the mass of the flask and water. Given data: Mass of water = 35.4 g, Mass of empty flask = 87.432 g. Therefore, mass of flask and water = 35.4 g + 87.432 g = 122.832 g.

**Step 2:** Add the rubber stopper to the flask. The total mass of the flask, water, and stopper is 146.72 g.

**Step 3:** Calculate the mass of the rubber stopper. Subtract the mass of the flask and water from the total mass: Mass of stopper = 146.72 g - 122.832 g = 23.888 g.

**Step 4:** Round the calculated mass to match the least precise measurement. In this case, as the mass of water was the least precise measurement with three significant figures, round the mass of the stopper to three significant figures: 23.9 g.

Therefore, the mass of the rubber stopper in the flask is 23.9 g.