Synthesis Reaction Packet
Equations
Name________________________________
Period________Date____________________
Chemical reactions are happening around you all the time. A match burns. A car rusts. Food spoils. Leaves decay. These are just a few chemical reactions.
Probably the most important chemical reactions take place in your body. They are happening this very moment. Digestion is a chemical process. So is respiration . In every one of your trillions of cells, chemical reactions are taking place all the time. Life depends upon chemical reactions.
There are several kinds of chemical reactions. One kind is a synthesis reaction. “Synthesis” means putting together . A synthesis reaction combines substances, usually elements (but sometimes smaller compounds), to form a new, larger compound. When the compound forms, we say it has been synthesized. Below is a “model” of a synthesis reaction.
A + B → AB
Element + Element → Compound
1. RUSTING When iron rusts, it combines with oxygen.
4Fe + 3O
2
→ 2Fe
2
O
3 iron + oxygen → iron oxide (rust)
Element + Element to form
Compound
2. THE BURNING OF CARBON Charcoal is made of the element carbon, C. When carbon burns, it combines with oxygen. This produces the gas carbon dioxide, CO
2
.
C + O
2
→ CO
2
carbon + oxygen
→ carbon dioxide
Element + Element Compound to form
A synthesis reaction is like any other kind of chemical reaction. No matter is created or destroyed. The atoms just change their arrangement.
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Look at the following equations and read the explanation. Then answer the questions.
When hydrogen explodes, it combines with oxygen and water is produced. The following equation shows what happens:
H
2
+ O
2
→ H
2
O hydrogen + oxygen → water
1. Hydrogen is an element / a compound.
(circle one) Oxygen is an element / a compound.
2. Water is an element / a compound.
3. Is the formation of water a synthesis reaction? _______ Why? ________________________________
When powdered sulfur and iron filings are heated together, they form iron (II) sulfide .
The following equation shows what happens:
Fe + S → FeS iron + sulfur → iron (II) sulfide
4. Iron is an element / a compound.
(circle one) Sulfur is an element / a compound.
5. Iron (II) sulfide is an element / a compound.
6. What happens to the iron and sulfur when they form iron sulfide? ______________________________
7. Why is the formation of iron (II) sulfide a synthesis reaction? _________________________________
___________________________________________________________________________________
8. In the synthesis of iron sulfide, which element is the metal? __________________________________
Na + Cl
2
→ 2NaCl sodium + chlorine → sodium chloride
9. Sodium is an element / a compound.
(circle one) Chlorine is an element / a compound.
10. Sodium chloride is an element / a compound.
11. What kind of reaction is the formation of sodium chloride? __________________ Why? __________
__________________________________________________________________________________
12. In the synthesis of sodium chloride, which element is the nonmetal? __________________________
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Naming: NaCl = sodium chloride
K
2
S = potassium sulfide
Name the following compounds:
FORMULA NAME
1.
2.
CaO
KI
3. NaBr
4.
5.
AgF
MgCl
2
Equation I: CO
2
+ C → 2CO
2
Equation II: CO
2
+ H
2
O → H
2
CO
3
1. How is Equation I different from the other synthesis equations seen in this packet? ________________
___________________________________________________________________________________
2. 1. How is Equation II different from the other synthesis equations seen in this packet? _____________
___________________________________________________________________________________
Look at the equations below. Identify the synthesis reactions by placing a check (√) next to it.
Equation
A Synthesis
Reaction
Not a Synthesis
Reaction
1. 2K + Br
2
→ 2KBr
2.
3.
2H
2
O → 2H
2
+ O
2
NaCl → Na + Cl
4.
5.
4Au + 3O
2
→ 2Au
2
O
3
2Na + 2HCl → 2NaCl + H
2
6.
7.
8.
9.
Cu + Br
2
→ CuBr
2
ZnSO
4
+ FeCl
2
→ ZnCl
2
+ FeSO
4
2Na + Br
2
→ 2NaBr
2HgO → 2Hg + O
2
10. CH
4
+ 2O
2
→ CO
2
+ 2H
2
O
3

Decomposition Reaction Packet
ChemCom Materials Unit C
Name________________________________
Period________Date____________________
Synthesis reactions build compounds. Anything that can be built can also ne taken apart. The breakdown of a compound into simpler substances is called decomposition . Decomposition is a chemical process.
Let’s look at two examples:
1. Common table salt (sodium chloride) is a compound composed of the elements sodium and chlorine . It
can be melted, and if electricity is passed through melted sodium chloride, it decomposes. It changes
back into atoms of sodium and chlorine. Here is the reaction:
2NaCl 2Na + Cl breaks it into
sodium chloride sodium chlorine
(compound) (element) (element)
heat
The decomposition of a compound by means of electricity is called electrolysis. Only certain
compounds can be decomposed by electrolysis. Usually these compounds are liquids.
2. Potassium chlorate (KClO
3
) is a compound composed of potassium, chlorine and oxygen. Heat
decomposes potassium chlorate into oxygen and potassium chloride (a simpler compound.) Here is the
reaction:
2KClO
3 breaks down into
2KCl + 3O
2
potassium chlorate potassium chloride oxygen
(compound) (a simpler compound) (element)
Notice that the decomposition is not complete, the oxygen has been separated, but the potassium and
chlorine are still joined in the compound, potassium chloride. Another kind of decomposition reaction
can separate potassium chloride into its elements. Only certain compounds can be decomposed with
4

Look at the diagram above and read page 4 . Electrolysis decomposes water. This is the equation for the reaction:
2H
2
O → 2H
2
+ O
2
water → hydrogen + oxygen
1. What is the formula for water? ___________
2. Water is a/an element / compound . (circle)
3. Name the elements that make up water: __________________ and ______________
4. Name the process that decomposes water: _____________________________
5. What kind of energy is used? _____________________.
6. When water decomposes, it changes into the elements ___________________ and ________________.
7. Water is in the solid / liquid / gaseous state.
8. Hydrogen is in the solid / liquid / gaseous state.
9. Oxygen is in the solid / liquid / gaseous state.
10. Which is simpler, water or the atoms that make up water? ___________________________________
11. Decomposition builds up / breaks down compounds.
12. Can electrolysis break down every compound? _____________
13. Name another compound that can be decomposed with electrolysis: ___________________________
14. A compound that can be separated by electrolysis must be in which state of matter? ______________
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Look at the diagram below: Mercury (II) oxide is a solid. Heat decomposes mercury (II) oxide into liquid mercury and oxygen gas This is the equation for the reaction:
2H g
O → 2H g
+ O
2
mercury (II) oxide → mercury + oxygen
15. What is the formula for mercury (II) oxide? _________________
16. Mercury (II) oxide is a(n) element / compound . (circle one)
17. Name the elements that make up mercury (II) oxide: ___________________ and ________________
18. What kind of energy decomposes mercury (II) oxide? ___________________
19. When mercury (II) oxide decomposes, it changes into the elements _____________ and ___________
20. Mercury (II) oxide is in the solid / liquid / gaseous state. (circle one)
21. Mercury is in the solid / liquid / gaseous state. (circle one)
22. Oxygen is in the solid / liquid / gaseous state. (circle one)
23. Which is simpler: mercury (II) oxide or the elements that make it up? __________________________
24. The mercury stays in the test tube / escapes into the air . (circle one)
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25. The oxygen stays in the test tube / escapes into the air . (circle one)
26. Can heat decompose every compound? __________
27. Name another compound that can be decomposed by heat: ___________________________
Completion: heating simpler potassium chlorate liquid mercury (II) oxide synthesis fewer water electrolysis molten sodium chloride decomposition
1. The combining of substances to form a compound is called _____________________________.
2. The breakdown of a compound into simpler substances is called ______________________________.
3. Two methods used to decompose compounds are ____________________ and __________________.
4. For a compound to decompose by electrolysis, it must be in the ____________________ state.
5. Two compounds that can be decomposed by electrolysis are ______________________________ and
__________________________________________.
6. Two compounds that can be decomposed by heat are ____________________________________ and
__________________________________________.
7. Atoms are __________________________ than molecules.
8. KCl is a simpler compound than KClO
3
because KCl has ____________________ elements and atoms.
Matching:
______ 1. synthesis reaction
______ 2. decomposition reaction
______ 3. electrolysis and heat
______ 4. electrolysis
______ 5. an element
A) breaks down compounds
B) uses electricity
C) methods of decomposition
D) simpler than a compound
E) builds compounds
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Identifying Synthesis and Decomposition Reactions:
1. CuCl
2
Equation
→ Cu + Cl
2
A Synthesis
Reaction
A Decomposition
Reaction
Neither
2.
3.
4.
5.
6.
3Hf + 2N
2
→ Hf
3
N
4
Zn + 2HCl → ZnCl
2
+ H
2
C
3
H
8
+ 5O
2
→ 4H
2
O + 3CO
2
2NaOH → 2Na + O
2
+ H
2
Fe + S → FeS
7. CaCl
2
+ FeSO
4
→ Ca SO
4
+ FeCl
2
4P + 5O
2
→ 2P
2
O
5
8.
9. 3CuCl
2
+ 2Al → 2AlCl
3
+ 3Cu
10. Ca(OH)
2
→ CaO + H
2
O
Short Answer:
1. Does boiling decompose water? ________________
2. What does boiling do to water? _________________________________________________________
___________________________________________________________________________________
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