Formulas and Reactions

Formulas and Reactions

Test is on Dec.13 and 15

Coefficients

This is the big number in front of a chemical formula. This number tells how many groups of that formula you have.

3 CO₂

The THREE in front of CO₂ is the coefficient.

Subscripts

The small number after the chemical formula. It only belongs to the element that it immediately follows and counts the amount of that element.

3 CO₂

The TWO after the chemical formula is the subscript.

Multiple Choice

Which is the correct formula for:
 three hydrogen (H)
one sulfur (S)
four oxygen (O)

• H₃SO₄
• HSO₄
• H₄S₃O
• H₂O

Multiple Choice

What is the coefficient for this formula? 9NaCl₂

• 9

• 2

• 1

• 11

Multiple Choice

CH₂Cu₈ - How many Copper atoms are in this formula?

• 1

• 2

• 8

• 16

Reactants

In a chemical equation, the reactants are on the left side of the arrow.

In this example

2Mg + O₂ --> 2MgO

• the reactants are 2Mg + O₂

• Reactants are always on the left.

Products

In a chemical equation, the products are on the right side of the arrow.

In this example

2Mg + O₂ --> 2MgO

• the product is 2MgO

• The products are always on the right.

Law of Conservation of Mass

Matter can not be created or destroyed, it only gets rearranged. In a chemical equation, the left side must be equal to the right side. The Reactants are equal to the Products.

Multiple Choice

$$C_2H_6\ +\ 5O_2\ \rightarrow\ 2CO_2\ +\ 3H_2O_2$$   Given this chemical equation, what are the PRODUCTS?

• $$C_2H_{6\ }and\ 5O_2$$  

• $$2CO_2\ and\ 3H_2O_2$$  

Multiple Choice

$$C_2H_6\ +\ 5O_2\ \rightarrow\ 2CO_2\ +\ 3H_2O_2$$   Given this chemical equation, what are the REACTANTS?

• $$C_2H_{6\ }and\ 5O_2$$  

• $$2CO_2\ and\ 3H_2O_2$$  

Multiple Choice

Which one is a compound?

• Co

• Br

• Fe

• CO

Multiple Choice

In chemical reactions, what does the principle of conservation of mass mean?

• Matter is not created or destroyed.

• The total mass of the reactants is greater than the total mass of the products.

• The total mass of the reactants is less than the total mass of the products.

• Matter is not changed.

Multiple Choice

The substances listed on the left side of a chemical equation are the

• Products

• Coefficients

• Precipitates

• Reactants

Multiple Choice

Which of the following reactions is balanced?

• 2CH₄ + O₂ -> CO₂ + H₂O

• CH₄ + 2O₂ -> CO₂ + H₂O

• CH₄ + 2O₂ -> CO₂ + 2H₂O

• None of the chemical equations are balanced.