Introduction to chemical reactions/balancing

NOTES: Balancing Chemical

Equations

Multiple Choice

What is the total number of atoms present in 5Na₃PO₄? (remember, a coefficient is a multiplier and Elements without a number is 1)

• 5

• 55

• 40

• 8

Multiple Choice

What is the little number after an element in a chemical equation called?

Example: H₂

• Coefficient

• Atom

• Subscript

• Equation

Multiple Choice

In the equation, 2Mg + O₂ ---> 2MgO, which are the reactants?

• Mg and O

• Mg and MgO

• MgO

• O and MgO

1.) Conservation of Mass

a.) Matter cannot be created nor
destroyed

b.) The mass on the left side (reactants)
MUST EQUALthe right side (products).

Multiple Choice

The compound ammonia is composed of nitrogen and hydrogen atoms. If two atoms of nitrogen completely react with six atoms of hydrogen to form two molecules of ammonia, which best describes the number of hydrogen atoms present in the two molecules of ammonia?

• 2

• 4

• 6

Multiple Choice

A chemistry teacher combines 20 grams of lemon juice with 25 grams of baking soda in a flask covered with a balloon. The flask and balloon have a combined mass of 105 grams. What is the mass of the entire setup after a reaction has occurred?

• 45 g

• 150 g

• 605 g

2.) Chemical Reaction Vocab

a.) Shown by chemical equations

4 Cu (s) + 1 O2 (g) → 2 Cu2O (s)

coefficients

subscripts

state of matter

2b.) Sides?

2Fe + O2 🡪 2FeO

Reactant(s)

Product(s)

“Rust”

2c.) Symbols in Equations

🡪

🡪🡪

s

L

g

aq

yields, produces, reacts to form

reversible reaction

heat is added

solid

Liquid (pure substance, Ex:Water)

gas

aqueous (dissolved in water)

3.) Why do Reactions Have to

be Balanced?

a.) To show that the law of conservation
of mass is satisfied.
b.) To know the proportions (amount of) the
elements and compounds react in.

4.) Balancing Equations Using

Atom Inventory

Zn + HBr → ZnBr2 + H2
_

a.) You can never change subscripts (determine bonding), only
coefficients (determine how many).
b.) You must change in the equation (on top) before adjusting
numbers below. The “inventory” (bottom) is just for counting.

_

_

_

Zn

H

Br

5.) Determine Atom “Inventory”

Li + AlCl3→ LiCl + Al

_

You must change in the equation (on top)
before adjusting numbers below. The
“inventory” (bottom) is just for counting.

_

_

_

What
elements do
we have?

6.) You Try!

NaF + O2→ Na2O + F2
_

You must change in the equation (on top) before adjusting
numbers below. The “inventory” (bottom) is just for counting.

_

_

_

7.) You Try!

Ga + CaBr2→ GaBr3 + Ca

_

You must change in the equation (on top) before adjusting
numbers below. The “inventory” (bottom) is just for counting.

_

_

_

Drag and Drop

Drag and drop the coefficients that balance this equation 2 $$Fe$$   + ​

Placeholder

$$Cl_2$$  ---->  ​

Placeholder

  $$FeCl_3$$  

Drag these tiles and drop them in the correct blank above

3

2

Multiple Choice

Balance this equation
_N₂ + _H₂ --> _NH₃

• 1,2,3

• 1,3,2

• 1,1,2

• 2,1,1

End of Balancing