Chemistry 4A

Which is the correct way to balance the chemical equation shown below?

Al + O₂ → Al₂O₃

• 2Al + O₂ → Al₂O₃

• 2Al + 3O₂ → Al₂O₃

• 4Al + 3O₂ → Al₂O₃

• 4Al + 3O₂ → 2Al₂O₃

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NGSS.MS-PS1-5

A experiment was conducted to test the law of conservation of mass. At the end of the experiment, only 82% of the mass of the initial reactants was present. The experiment was repeated three times with similar results. Which best explains why some of the mass was lost?

• The mass escaped as a gas.

• The mass transformed into a liquid.

• The mass remained part of the reactant.

• The mass turned into a heavier chemical.

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NGSS.MS-PS1-2

NGSS.MS-PS1-5

Which of the following is a correctly written chemical equation that demonstrates the conservation of mass?

• Mg + HCl ---> H₂ + MgCl₂

• H₂O + CO₂ ---> H₂CO₃

• KClO₃ ---> KCl + O₂

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NGSS.MS-PS1-5

A teacher has 100 g of Reactant X and 150 g of Reactant Y for her class demonstration. After combining the two reactants, how much product should she have?

• 50 g

• 100 g

• 150g

• 250g

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NGSS.MS-PS1-5

Two substances react and the mass is recorded. The mass of the products does not equal the mass of the reactants. Which is the best explanation for the difference in the masses?

• The scale was not balanced.

• Some of the mixture spilled.

• Gas was produced and lost to the environment.

• Substances were added after the initial mass was recorded.

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NGSS.MS-PS1-2

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How does the concept of conservation of mass apply to chemical reactions?

• The reactants and products have exactly the same atoms.

• The reactants and products have exactly the same molecules.

• The change in the amount of matter is equal to the change in energy.

• The change in the amount of matter is only a small percentage of the total mass.

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NGSS.MS-PS1-5

A chemistry teacher combines 20 grams of lemon juice with 25 grams of baking soda in a flask covered with a balloon. The flask and balloon have a combined mass of 105 grams. What is the mass of the entire setup after a reaction has occurred?

• 45 grams

• 150 grams

• 605 grams

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NGSS.MS-PS1-2

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Substance A has a mass of 7 grams. When substance A was mixed with substance B, a new substance was formed. Which statement best describes the Law of Conservation of Mass?

• The mass of substance B is equal to the mass of the product.

• The mass of the product is equal to the mass of the reactants.

• The mass of the product is less than the mass of the reactants.

Tags

NGSS.MS-PS1-5

The reaction below takes place in a closed system.

CaCO₃ ---> CaO + CO₂

Which best describes this balanced equation?

• More products and less reactants are produced.

• More reactants and less products are produced.

• Reactants and products are equal in the chemical reaction.

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NGSS.MS-PS1-2

NGSS.MS-PS1-5

If a chemical reaction such as photosynthesis begins with 6 atoms of carbon (C), how many atoms of carbon (C) should be in the products?

• 12 atoms of carbon (C)

• 6 atoms of carbon (C)

• 3 atoms of carbon (C)

• 2 atoms of carbon (C)

Tags

NGSS.MS-PS1-5