Download Analyzing Chemical Equations ANSWER KEY

Analyzing Chemical Equations Answer Key
1. Propane burns. Propane combines with oxygen in the air to make carbon dioxide and water vapor. This
chemical reaction takes place when a “gas” grill is used for cooking.
CH3 + 2O2 → CO2 + 2H2O
Which chemical formula(s) represents the
reactants?
Which chemical formula(s) represents the
products?
CH3 and 2O2
CO2 and 2H2O
How many atoms of each element are
How many atoms of each element are
present in the reactants?
present in the products?
C–1
C–1
H–3
H–4
O–4
O–4
Is this a balanced equation? Explain. NO. The number of H atoms is not equal in the
reactants and the products.
2. An iron bar rusts. The iron reacts with oxygen in the air to make rust.
4Fe + 3O2 → 2Fe2O3
Which chemical formula(s) represents the
reactants?
Which chemical formula(s) represents the
products?
4Fe and 3O2
2Fe2O3
How many atoms of each element are
How many atoms of each element are
present in the reactants?
present in the products?
Fe – 4
Fe – 4
O– 6
O–6
Is this a balanced equation? Explain. YES! The # of atoms in the reactants and products
are equal.
3. A silver spoon tarnishes. The silver reacts with sulfur in the air to make silver sulfide, the black material
we call tarnish.
2Ag + S → Ag2S
Which chemical formula(s) represents the
reactants?
Which chemical formula(s) represents the
products?
2Ag + S
Ag2S
How many atoms of each element are
present in the reactants?
How many atoms of each element are
present in the products?
Ag – 2
Ag – 2
S–1
S–1
Is this a balanced equation? Explain. Yes! The number of atoms for each element is equal
in the reactants and the products.
4. Living cells obtain energy from glucose molecules through the process of respirations which is the
breakdown of glucose to obtain energy.
C6H12O6 + 6O2 → 6CO2 + 6H2O + energy
Which chemical formula(s) represents the
reactants?
Which chemical formula(s) represents the
products?
C6H12O6 + 6O2
6CO2 + 6H2O
How many atoms of each element are
How many atoms of each element are
present in the reactants?
present in the products?
C–6
C–6
H – 12
H – 12
O – 18
O – 18
Is this a balanced equation? Explain. YES! The number of atoms for each element is
equal in the reactants and the products.
5. Plant cells use water, carbon dioxide, and energy from the sun to produce glucose and oxygen. This
process is called photosynthesis.
CO2 + H2O + energy → C6H12O6 + O2
Which chemical formula(s) represents the
reactants?
Which chemical formula(s) represents the
products?
CO2 + H2O
C6H12O6 + O2
How many atoms of each element are
present in the reactants?
How many atoms of each element are
present in the products?
C–1
H–2
O–3
C–6
H – 12
O–8
Is this a balanced equation? Explain. NO! The number of atoms for each element is not
equal in the reactants and products.
6. When mixed, vinegar (acetic acid) and baking soda (sodium bicarbonate) eventually produces sodium
acetate, water and carbon dioxide.
2NaHCO3 + CH3COOH → CH3COONa + H2O + CO2
Which chemical formula(s) represents the
reactants?
Which chemical formula(s) represents the
products?
2NaHCO3 + CH3COOH
CH3COONa + H2O + CO2
How many atoms of each element are
How many atoms of each element are
present in the reactants?
present in the products?
Na – 2
Na – 1
H–6
H–5
C–4
C–3
O–8
O–5
Is this a balanced equation? Explain. No. The # of atoms for each element is NOT equal
in the reactants and the products.
7. Carbon and oxygen react to create carbon monoxide. Carbon monoxide is very usefull in the chemical
industry, but it can also be deadly to animals, due to its ability to interfere with the delivery of oxygen in
our blood.
2C + O2 → CO
Which chemical formula(s) represents the
reactants?
Which chemical formula(s) represents the
products?
2C + O2
CO
How many atoms of each element are
present in the reactants?
How many atoms of each element are
present in the products?
C–2
O–2
C–1
O–1
Is this a balanced equation? Explain. NO! The # of atoms for each element is NOT equal
in the reactants and the products.
8. Silicon, the second most common element in the Earth’s crust, is commonly used in semiconductors.
Since it is naturally found in quartz, it is necessary to heat the quartz with carbon to separate the silicon.
SiO2 + 2C → Si + 2CO
Which chemical formula(s) represents the
reactants?
Which chemical formula(s) represents the
products?
SiO2 + 2C
Si + 2CO
How many atoms of each element are
present in the reactants?
How many atoms of each element are
present in the products?
Si – 1
O–2
C–2
Si – 1
O–2
C–2
Is this a balanced equation? Explain. YES! The # of atoms are all equal.