Unit 2 Study Guide

Law of Conservation of Mass: State the Law of Conservation of Mass.

• Mass is neither created nor destroyed in a chemical reaction; it is conserved.

• Energy is always conserved but mass may be lost.

• Atoms can change into energy during ordinary reactions.

• Mass often decreases because gases escape.

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Law of Conservation of Mass: How does this law apply to chemical reactions in closed systems?

• The total mass of reactants equals the total mass of products.

• Products always have greater mass than reactants.

• Mass decreases as heat is released.

• Only gaseous reactions follow the law.

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Law of Conservation of Mass: What evidence supports the conservation of mass during a reaction?

• Measured mass of the system is the same before and after the reaction.

• The solution changes color.

• The temperature increases during the reaction.

• Bubbles are produced.

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Law of Conservation of Mass: If 15 g of reactants produce 12 g of products, what might explain the discrepancy?

• The reaction occurred in an open system and some product escaped as a gas.

• Energy converted into mass, reducing product mass.

• Atoms were destroyed during the reaction.

• The reaction was balanced, so mass should increase.

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Law of Conservation of Mass: How does the law relate to balancing chemical equations?

• Balancing ensures the same number of each type of atom on both sides of the equation.

• Balancing determines the speed of the reaction.

• Balancing predicts physical states of substances.

• Balancing eliminates the need for catalysts.

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Law of Conservation of Mass: Which experiment best demonstrates mass conservation?

• Carrying out a reaction in a sealed container and verifying the mass before and after is unchanged.

• Performing a reaction in an open beaker and observing that the mass is higher at the end.

• Heating a sealed container and noting that the mass increases with temperature.

• Letting a gas escape and showing that mass changes randomly.

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Law of Conservation of Mass: Why is mass conserved even when substances change state?

• Particles are rearranged but not created or destroyed.

• Mass converts to energy when state changes.

• Volume remains constant, so mass is constant.

• Temperature is fixed, so mass cannot change.

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Law of Conservation of Mass: What role does this law play in industrial chemical processes?

• It allows accurate yield calculations and material balances for scaling processes.

• It determines the color of the final product.

• It eliminates waste entirely without planning.

• It replaces the need for safety protocols.

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Law of Conservation of Mass: How would you explain this law to someone unfamiliar with chemistry?

• In a closed system, what goes in must equal what comes out in terms of mass.

• Matter can appear and disappear during reactions.

• Reactions usually create mass from energy.

• Mass is conserved only for solid substances.

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Law of Conservation of Mass: What happens to mass in a reaction conducted in an open container?

• Measured mass may decrease because gaseous products can escape.

• Mass always increases because air enters the container.

• Mass is unaffected by whether the container is open or closed.

• The law does not apply to open systems and is invalid.

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