A student investigates the conservation of mass during chemical reactions using the two setups shown below:
In Setup 1, iron wool is heated in an open crucible, and the mass of the solid residue is measured before and after heating. In Setup 2, the same mass of iron wool is heated inside a sealed glass conical flask containing air, and the total mass of the flask and its contents is monitored on a digital balance.
Which of the following describes the correct observation and explanation for each setup?
In Setup 1, the measured mass of the solid increases because the iron reacts with oxygen from the surrounding air. In Setup 2, the total mass recorded on the balance remains constant because the system is closed.
In Setup 1, the measured mass of the solid increases because the iron reacts with nitrogen from the surrounding air. In Setup 2, the total mass recorded on the balance increases as the reaction progresses.
In Setup 1, the measured mass of the solid increases because the iron reacts with oxygen from the surrounding air. In Setup 2, the total mass recorded on the balance decreases as gas inside is consumed and converted to a solid.
In Setup 1, the measured mass of the solid decreases as thermal energy drives off gaseous impurities. In Setup 2, the total mass recorded on the balance remains constant because the system is closed.