Chemistry Unit 1B

Why must chemical equations be balanced?

Matter cannot be created or destroyed, so the number of atoms for each element must stay the same on both sides of the equation.

How can you balance chemical equations?

With coefficients.

What are evidences that a chemical reaction has occurred?

Production of gas, heat, and light. Color or oder change. Formation of a precipitate.

What is a precipitate? (L1)

The formation of a solid from a solution.

What must be happening at a molecular level for a chemical reaction to have occurred?

Bonds have to be broken and/or formed, creating new substances.

What does a coefficient represent?

Individual molecules that are not bonded together.

What does a subscript represent?

How many atoms of the element are in one bonded molecule.

What does aq mean? (L2)

Aqueous: a substance has been dissolved in water. An aqueous solution is a mixture of particles of that substance with molecules of water.

Energy written on the product side means the equation is what? (L2)

Exothermic (Pex).

Energy written on the reactant side means the equation is what? (L2)

Endothermic (Ren).

When writing chemical reactions, diatomic elements are always written as what when alone? (L3)

O2, H2, F2, etc (they have their 2 subscript).

What reactions have 2 or more reactants that produce one product? (L4)

Synthesis.

What reactions have one reactant that breaks into 2 or more products? (L4)

Decomposition.

What reactions have a single element and a compound as the reactants, and during the reaction, the single element replaces part of the compound? In the products, there is a new single element and a new compound. (L4)

Single Replacement.

What reactions have two compounds as the reactants, and during the reaction, the compounds switch partners, creating 2 new compounds as the products? (L4)

Double Replacement.

What reactions have a compound with C, H, or C,H, and O, reacting with oxygen gas to produce carbon dioxide and water? (L4)

Combustion.

According to the activity series, a single replacement reaction will occur if what? (L6)

The single element on the reactant side is higher on the list than the original element inside the compound.

In a single replacement reaction, if the new single element on the product side is a metal, then what forms during the reaction? (L6)

A precipitate.

What do you use to tell if a reaction occurred in a double-replacement equation?

Solubility Rules.

What does insoluble mean? (L7)

Substances that do not dissolve in water.

When drawing an ionic compound dissolving in water, what will always stay the same? (L7)

The ratio of cation to anion.

What happens to a compound with a polyatomic ion when it becomes aqueous? (L7)

Polyatomic ions in these compounds will separate from other ions, but the atoms in the polyatomic ion will not break apart since they are covalently bonded together.

Before writing ionic or net ionic equations, your chemical equation must be what? (L9)

Balanced.

In an ionic or net ionic equation, what type of ions are broken up and written as individual ions? (L9)

All aqueous (aq).

When aq atoms are broken apart in ionic or net ionic equations, what must be shown? (L9)

Their charge.

What happens to a compound with a (s), (l), or (g) in an ionic or net ionic equation? (L9)

They will remain written as the original equation with no charge shown.

When writing Na(2)CO(3) (aq) as a total ionic equation, what happens to the subscripts? (L9)

The subscripts turn into coefficients, so it becomes 2Na and 3CO.

In a net ionic equation, what happens to ions that match each other on the reactant and product sides? (L9)

They are cancelled out and not written in the net ionic equation.

What are the ions that get cancelled out in the net ionic equations called? (L9)

Spectator ions because they remain in the solution unchanged during the reaction.

What happens if all ions are cancelled out and no substances remain in the net ionic equation? (L9)

No reaction occurs.

What needs to happen in a double replacement equation for a reaction to happen?

There needs to be one (aq) compound and one (s) precipitate compound.