Question

name date secured (s2) lo: swbat observe cause-and-effect relationships and develop explanations supported by data and evidence to explain how mass is conserved in chemical reactions 1. which of the following best explains the mass of products in the reaction 2h₂ + o₂ → 2h₂o? a the mass of water produced is less than the mass of hydrogen and oxygen combined. b. the mass of water produced is equal to the mass of hydrogen and oxygen combined. c. the mass of water produced is greater than the mass of hydrogen and oxygen combined. d. the mass of water produced does not relate to the reactants’ mass. 2. sarah and michael are conducting an experiment in their science class to study the reaction between vinegar (acetic acid) and chalk (calcium carbonate). they carefully measure 5 grams of chalk and place it in a beaker containing 50 ml of vinegar. as soon as the chalk touches the vinegar, they observe vigorous bubbles forming. the following equation can represent the reaction occurring: caco₃ + 2ch₃cooh → ca(ch₃coo)₂ + h₂o + co₂ sarah and michael measure the mass of the beaker and its contents before and after the reaction. to their surprise, they find that the total mass has decreased slightly. image of a beaker with vinegar and bubbles which of the following best explains why the total mass of the system decreases slightly during this reaction? a. the chalk dissolves, reducing its mass. b. the vinegar evaporates, reducing the liquid’s mass. c. the bubbles contain a gas that escapes into the air. d. the reaction creates a new substance with less mass. 3. jamal is curious about how burning a candle affects its mass. for his science fair project, he designed an experiment to investigate the conservation of mass when a candle is burning. he sets up the following apparatus:

Explanation:

Question 1

The law of conservation of mass states that in a chemical reaction, the total mass of reactants equals the total mass of products. In the reaction \(2H_2 + O_2
ightarrow 2H_2O\), hydrogen (\(H_2\)) and oxygen (\(O_2\)) are reactants, and water (\(H_2O\)) is the product. So the mass of water produced should equal the combined mass of hydrogen and oxygen. Option A is wrong (mass should not be less), C is wrong (mass should not be greater), D is wrong (mass is related via conservation of mass).

The reaction \(CaCO_3 + 2CH_3COOH
ightarrow Ca(CH_3COO)_2 + H_2O + CO_2\) produces \(CO_2\) gas (the bubbles). If the system (beaker and contents) is not sealed, the \(CO_2\) gas escapes into the air, so the measured mass of the system decreases. Option A: Chalk reacts, not just dissolves, and mass conservation still holds (reactants' mass = products' mass, but gas escapes). Option B: Evaporation of vinegar is not the main reason for the mass decrease here (the reaction produces gas). Option D: Reactions conserve mass, so new substances' total mass should equal reactants' mass (but gas escapes, so measured mass decreases, not that new substance has less mass).

Answer:

B. The mass of water produced is equal to the mass of hydrogen and oxygen combined.

Question 2