Chemical Reactions Unit Review

A teacher does a reaction with baking soda and vinegar. She measures the mass of the reactants before the experiment, mixes the baking soda and vinegar together in an open test tube, and then measures the mass of the products after the experiment. She notices the mass of the products is less than the mass of the reactants. What most likely explains the difference in the mass before and after the reaction?

• A gas was produced in the reaction that escaped because the reaction was in an open system.

• A precipitate was formed and it left because the reaction was in a closed system.

• The temperature of the reactants was lower than the products.

• Some matter was destroyed in the chemical reaction.

Answer explanation

The mass of the products is less than the mass of the reactants because a gas was produced in the reaction that escaped due to the reaction being in an open system.

Tags

7-PS1-5

Is the diagram showing a balanced or unbalanced equation?

• Balanced

• Unbalanced

• It is not possible to tell

• The reaction is both balanced and unbalanced

Answer explanation

The diagram shows a balanced equation because the reaction has an equal number of atoms on both sides.

Tags

NGSS.MS-PS1-2

NGSS.MS-PS1-5

The chemical formula for nitric acid is HNO₃. What composes this compound?

• helium atom, 1 nitrogen atom, and 3 osmium

• hydrogen atom, 1 sodium atom, and 3 oxygen atoms

• helium atom, 1 sodium atom, and 3 osmium atoms

• hydrogen atom, 1 nitrogen atom, and 3 oxygen atoms

Answer explanation

Nitric acid is composed of 1 hydrogen atom, 1 nitrogen atom, and 3 oxygen atoms. This combination forms the chemical formula HNO₃, which represents nitric acid.

Tags

7-PS1-5

The chemical equation for a combustion reaction is shown. What is the number of hydrogen atoms on the reactant side?

• 1

• 2

• 6

• 12

Answer explanation

The number of hydrogen atoms on the reactant side is 2, as there are 2 molecules of H2 in the reactants.

Tags

7-PS1-5

Which of the following is a synthesis reaction?

• 2H₂O --> 2H₂ + O₂

• Fe + CuSO₄ --> FeSO₄ + Cu

• Cu + SO₄ --> CuSO₄

• Zn + 2HCl --> ZnCl₂ + H₂

Answer explanation

A synthesis reaction is when two or more substances combine to form a single product. In this case, the correct choice is Cu + SO4 -> CuSO4, where copper and sulfate combine to form copper sulfate.

Tags

NGSS.MS-PS1-5

Baking bread and cooking an egg are examples of....?

• Endothermic processes

• Exothermic processess

• None of these 

Answer explanation

Baking bread and cooking an egg are examples of endothermic processes.

Tags

NGSS.MS-PS1-4

NGSS.MS-PS3-4

Two or more substances that are mixed together but not chemically combined is a(n) ___

• compound

• mixture

• element

• atom

Answer explanation

A mixture is a combination of two or more substances that are not chemically combined.

In this chemical reaction, which is the product/s?

• magnesium

• magnesium and oxygen

• magnesium oxide

• oxygen

Tags

NGSS.MS-PS1-2

What is the conservation of mass?

• mass of reactants > mass of products

• mass of reactants < mass of products

• mass of reactants = mass of products

Tags

NGSS.MS-PS1-5

When energy is transferred from the substances to the surroundings during a chemical reaction, what type of reaction is this?

• endothermic

• exothermic

• decomposition

• combustion

Tags

NGSS.HS-PS1-4

NGSS.HS-PS3-4