Conservation of mass Transitional Reasoning Download PDF

Questions

1. 1.

   A student places an airtight flask containing calcium carbonate and a small vial of hydrochloric acid onto a digital balance, recording an initial mass of 185.4 g. After tilting the flask to mix the reactants, vigorous bubbling occurs and a gas fills the sealed container, while the balance reading remains unchanged at 185.4 g. When the student subsequently removes the stopper, gas escapes with an audible hiss, and the balance reading drops to 183.2 g. Which statement correctly evaluates these observations according to the law of conservation of mass?

   • A) The chemical reaction violated the law of conservation of mass because the final mass of the container was lower than its initial mass.
   • B) Gaseous products possess no measurable mass while trapped inside a container, so mass was only accounted for after opening.
   • C) Mass was strictly conserved throughout the chemical change, and the apparent mass decrease occurred solely because gaseous matter escaped into the surrounding air.
   • D) A total of 2.2 g of matter was permanently destroyed during the reaction and converted entirely into non-material thermal energy.