Chemical Equations and Conservation of Mass

Mia is conducting an experiment to create water in the lab. The model of the chemical equation for the formation of water she uses supports which of the following statements?

• New matter can be created.

• The mass of the reactants is the same as the mass of the products.

• The chemical equation is not balanced.

• Water can be a solid, a liquid, or a gas.

Priya is conducting an experiment in her chemistry class. She needs to identify which chemical equation is balanced, meaning it conserves atoms. Can you help her?

• N₂ + H₂ → 2NH₃

• 2N₂ + 2H₂ → 4NH₃

• 2N₂ + 3H₂ → 2NH₃

• N₂ + 3H₂ → 2NH₃

Liam is conducting an experiment in his chemistry class. He uses the balanced chemical equation shown to determine how many sodium chloride (NaCl) compounds would result from combining 6 sodium (Na) atoms with 3 chloride (Cl2) molecules.

• 3 NaCl

• 2 NaCl

• 6 NaCl

• This cannot be determined with the information provided.

William is conducting an experiment to understand the law of conservation of mass. He starts with a certain number of oxygen molecules. In order for the chemical reaction to obey the law of conservation of mass, how many total oxygen atoms would be present in the products?

• 8

• 10

• 12

• 16

A chemical reaction is modeled by the particle diagram provided. Students developed a few representative chemical equations for the information provided in the model and were asked to determine if the reaction obeys the law of conservation of mass. Which chemical equation is an accurate representation of the model, and which claim is supported by the model?

• 6X + 3Y → 6XY

• 6X₂ + 3Y₂ → 6X₂Y

• 12X + 6Y → 6X₂Y

• Claim: The reaction obeys the law of conservation of mass.

• Claim: The reaction does not obey the law of conservation of mass.

Daniel is conducting an experiment where he observes the reaction between magnesium and oxygen. Use the image of the reaction above to choose the balanced equation that accurately reflects the model.

• Mg + 2O → MgO₂

• Mg₂ + O₂ → 2MgO

• 2Mg + O₂ → 2MgO

• Mg₂ + O → Mg₂O

Olivia and David are conducting an experiment with Magnesium (Mg) and Oxygen (O). Magnesium is represented by purple circles and Oxygen is represented by red circles. Which of the following statements supports the correct equation for their experiment?

• Oxygen is represented as a molecule and therefore has a subscript of 2 in the chemical equation.

• Magnesium is represented as a molecule and therefore has a subscript of 2 in the chemical equation.

• Neither oxygen nor magnesium should have subscripts in the equation because they are not represented as molecules.

• Magnesium oxide should have a subscript because it is a compound.

Maya and her friends are discussing different types of nuclear reactions in their science class. Which nuclear reaction is not very useful because it is very difficult to control?

• Fusion

• Beta decay

• Positron emission

• Fission

Abigail is learning about nuclear power plants in her science class. She wonders, how does nuclear fission create electricity?

• The atom splits, releasing energy that is used for electricity.

• The atoms splits, releasing neutrons that are used for electricity.

• The energy that is released creates steam for generators to make electricity.

• The neutrons that are released power generators that make electricity.

Abigail is studying ancient artifacts and wants to determine their age. What process should she use for radioactive dating?

• Nuclear fission

• Gamma decay

• Half-life

• Positron emission