If you place a 4.00 g effervescent antacid pill into 85 mL (85 g ) of water in a 90 g glass, how much will the glass of water weigh once the antacid pill has dissolved?

The glass of water weigh once the antacid pill has dissolved will be less than the 179 grams due to evolution of carbon dioxide.

Explanation:

Mass of effervescent antacid pill = 4.00 g

Mass of water = 85 g

Mass of glass = 90 g

Total mass of the substances  together : 4.00 g + 85 g + 90 g = 179 g

Effervescent antacid pill , moment it get dissolved in water carbon dioxide gas is evolves and escape from the solutions.

This means that mass of the weight of the glass of water with antacid dissolved in it will be less than 179 grams.