Question

abby added baking soda and vinegar to a flask. she stretched a balloon over the opening of the flask. after several minutes, she noticed small bubbles rising along the side of the flask as the balloon slowly began to inflate. the mass of the flask/balloon complex after the reaction would weigh more since something new was created. the mass of the flask/balloon complex after the reaction should be less since a gas was created. the mass of the flask/balloon complex after the reaction should be less because the reactants are used up during the chemical reaction. the mass should be the same since... (image: before and after flask with balloon, gas label)

Explanation:

This problem relates to the law of conservation of mass in a chemical reaction. The system (flask, balloon, reactants, and products) is closed (the balloon traps the gas produced). According to the law of conservation of mass, matter is neither created nor destroyed in a chemical reaction, so the total mass of the system remains the same. The gas produced is still part of the system (trapped in the balloon), so the mass of the flask/balloon complex should be the same before and after the reaction. The other options are incorrect: the first implies mass is created (violates conservation), the second implies mass is lost (but gas is trapped, so mass remains), and the third incorrectly states reactants are used up to imply less mass (but products, including gas, have mass too).

Answer:

The mass should be the same since matter is conserved in a chemical reaction (the gas produced is trapped in the balloon, so total mass of the system remains unchanged). (The option stating "The mass should be the same since..." is the correct one, though the exact option label isn't fully visible, but the reasoning is based on conservation of mass.)