Question

in an experiment, students first weigh their equipment, a flask and a balloon, and then measure... they mix the reactants in the flask and quickly cover the flask with a balloon. the mixture bubbles... weigh the whole system. the table shows their data. table: baking soda (mass missing), vinegar 5, flask 55, balloon 9, mass of system after reaction 70 which valid conclusion is best supported by the data? a. mass is conserved during a chemical reaction. b. the mass of the equipment is always greater than the mass of the reactants. c. bubbles form when a clear liquid mixes with a white powder in a sealed container. d. baking soda and vinegar can also exist as gases and fill up a balloon that is sealing a system.

Explanation:

1. First, calculate the total mass of reactants and equipment before the reaction. The mass of vinegar is 5 g, flask is 55 g, balloon is 9 g, and let's assume baking soda's mass (let's find it from the after - reaction mass). Wait, actually, the total mass before reaction: let's denote baking soda mass as \( m_{bs} \). The total mass before reaction is \( m_{bs}+5 + 55+9=m_{bs}+69 \). The mass after reaction is 70 g. But actually, we can think about the law of conservation of mass. In a closed system (the flask and balloon), the mass should be conserved. Let's check the sum of known masses: if we assume that the baking soda's mass plus vinegar (5g) + flask (55g)+balloon (9g) should equal the mass after reaction (70g). So \( m_{bs}+5 + 55+9=70 \), so \( m_{bs}=70-(5 + 55+9)=1 \)g. Then the total mass before reaction is \( 1+5 + 55+9 = 70 \)g, which is equal to the mass after reaction. This shows that mass is conserved in the chemical reaction (baking soda and vinegar reacting) in this closed system.
2. Option B: There's no basis for saying the mass of equipment is always greater than reactants. For example, if reactants are very massive, this won't hold.
3. Option C: The formation of bubbles is an observation, not a conclusion about mass or chemical reaction principles, and the question is about a conclusion supported by the data (mass data), so C is not relevant.
4. Option D: Baking soda (a solid) and vinegar (a liquid) react to form a gas (like \( CO_2 \)), but they themselves don't exist as gases in this context to fill the balloon; the product gas does. So D is incorrect.

Answer:

A. Mass is conserved during a chemical reaction.