Unit 5 Exam

Why must chemical equations be balanced?

• So that the equation doesn't explode

• The reaction won't happen until it is balanced

• Based on the Law of Conservation of Matter, matter cannot be created or destroyed.

• Based on the Law of Conservation of Energy, energy cannot be created or destroyed.e

Chemical reactions occur when _________ are broken and new bonds are formed.

• mixtures
• osteoclasts
• physical bonds
• chemical bonds

Which of the following is NOT an indication of a chemical reaction?

• new gas formed

• temperature change

• new smell detected

• two liquids form a mixture

The products of a reaction have the same ________as the reactants.

• molecule

• atoms

• subscripts

• coefficients

Chemical reactions

• create and destoy atoms

• only occurs outside living organisms

• occurs only in living organisms

• produce new substances

Chemical equations

• give directions for naming compounds

• describe only biological changes

• describe chemical reactions

• show how to write formulas

Which side of a chemical equation is the product side?

• Left (before the yields sign)
• Right (after the yields sign)

What is a coefficient?

• The small number on the right of the chemical symbol.
• The large number to the left of a formula.

How many atoms of aluminum are on each side of the following equation: 4Al + 3O₂ --> 2Al₂ O₃

• 2
• 6
• 1
• 4

At the end of chemical reactions, what is the total mass of the reactants compared to the total mass of the products?

• the product is doubled
• the product is half the mass of the reactants
• the mass is the same
• the mass changes depending on the reaction