Question
A group of students wants to observe the reaction between magnesium metal and hydrochloric acid. They place a 1.2-g strip of the metal into a test tube containing 4.7 g of aqueous hydrochloric acid. The students observe bubbles forming on the surface of the metal, and the solution turns white. After all of the metal disappears, they use a triple-beam balance to determine the mass of the products. The resulting mass is less than the mass of the reactants, which leads them to believe they did something incorrectly during their experiment.
Examine the equation below, then determine which of the following steps the students could have taken to prove that mass was conserved during the reaction.
Mg(s) + HCl(aq) ⇒ H2(g) + MgCl2(aq)
A.
The students could boil the solution that formed to remove excess water, weigh the solid magnesium chloride, then compare that mass to the mass of the reactants.
B.
The students could hold a glowing splint over the top of the test tube to check for the presence of hydrogen gas.
C.
The students could recalibrate the triple-beam balance before finding the mass of the solution again.
D.
The students could have collected the hydrogen gas formed during the reaction, found its mass, and added that amount to the mass of the solution.
Examine the equation below, then determine which of the following steps the students could have taken to prove that mass was conserved during the reaction.
Mg(s) + HCl(aq) ⇒ H2(g) + MgCl2(aq)
A.
The students could boil the solution that formed to remove excess water, weigh the solid magnesium chloride, then compare that mass to the mass of the reactants.
B.
The students could hold a glowing splint over the top of the test tube to check for the presence of hydrogen gas.
C.
The students could recalibrate the triple-beam balance before finding the mass of the solution again.
D.
The students could have collected the hydrogen gas formed during the reaction, found its mass, and added that amount to the mass of the solution.
Answers
GPT-4o mini
To determine which step the students could take to prove that mass was conserved during the reaction, we need to consider the nature of the reaction and the conservation of mass principle.
The reaction between magnesium and hydrochloric acid produces hydrogen gas and magnesium chloride. If the resulting mass is less than the mass of the reactants, it is likely due to the hydrogen gas being released into the atmosphere during the reaction. Therefore, measuring all products—including the gas produced—is necessary to confirm the conservation of mass.
Let's evaluate the options:
**A.** The students could boil the solution that formed to remove excess water, weigh the solid magnesium chloride, then compare that mass to the mass of the reactants.
- This option does not account for the hydrogen gas that escaped during the reaction. Thus, while it measures some of the products, it fails to confirm that all mass was conserved.
**B.** The students could hold a glowing splint over the top of the test tube to check for the presence of hydrogen gas.
- This would indicate that hydrogen gas is being produced, but it doesn't provide quantitative data to prove mass conservation.
**C.** The students could recalibrate the triple-beam balance before finding the mass of the solution again.
- While recalibrating the balance is good practice, it does not address the issue of gas loss during the reaction.
**D.** The students could have collected the hydrogen gas formed during the reaction, found its mass, and added that amount to the mass of the solution.
- This option allows for the measurement of the mass of all products (including the gas), which directly addresses the conservation of mass by adding the mass of the solid products and the mass of the collected gas.
The best choice to demonstrate mass conservation in the experiment is **D.**
The reaction between magnesium and hydrochloric acid produces hydrogen gas and magnesium chloride. If the resulting mass is less than the mass of the reactants, it is likely due to the hydrogen gas being released into the atmosphere during the reaction. Therefore, measuring all products—including the gas produced—is necessary to confirm the conservation of mass.
Let's evaluate the options:
**A.** The students could boil the solution that formed to remove excess water, weigh the solid magnesium chloride, then compare that mass to the mass of the reactants.
- This option does not account for the hydrogen gas that escaped during the reaction. Thus, while it measures some of the products, it fails to confirm that all mass was conserved.
**B.** The students could hold a glowing splint over the top of the test tube to check for the presence of hydrogen gas.
- This would indicate that hydrogen gas is being produced, but it doesn't provide quantitative data to prove mass conservation.
**C.** The students could recalibrate the triple-beam balance before finding the mass of the solution again.
- While recalibrating the balance is good practice, it does not address the issue of gas loss during the reaction.
**D.** The students could have collected the hydrogen gas formed during the reaction, found its mass, and added that amount to the mass of the solution.
- This option allows for the measurement of the mass of all products (including the gas), which directly addresses the conservation of mass by adding the mass of the solid products and the mass of the collected gas.
The best choice to demonstrate mass conservation in the experiment is **D.**