Synthesis Reactions

A synthesis reaction involves two or more substances reacting to produce a single product. Reactants can be any combination of elements and compounds:

- two different elements which form a binary compound- an element and a compound which form a new compound- two compounds which form a new compound

The general form of a synthesis reaction is A + B ---> AB

Types of Synthesis Reactions:

Types ExamplesExamples

1) Two different elements form a binary compound1) Two different elements form a binary compound1) Two different elements form a binary compound

a) metal + non-metal form an ionic compound

- transfer of electrons from metal to non-metal- predict the product following

nomenclature rules- Remember that multivalent metals can create

multiple products

b) two non-metals form a covalent/molecular compound

- electrons are shared, so there are no ions to determine the product

Write the balanced equation that shows the synthesis reaction between potassium metal & fluorine gas:potassium + fluorine ---> potassium fluoride2 K(s) + F2(g) ---> 2 KF(s)

Write the balanced equation that shows the synthesis of reaction between iron & oxygen (remember iron has 2 possible oxidation states, 3+ & 2+):iron + oxygen ---> iron (III) oxide4 Fe(s) + 3 O2(g) ---> 2 Fe2O3(s)oriron + oxygen ---> iron (II) oxide2 Fe(s) + O2(g) ---> 2 FeO(s)

Write the balanced equation for the synthesis reaction between sulfur & oxygen (common oxide of sulfur is sulfur dioxide):sulfur + oxygen ---> sulfur dioxideS8(s) + 8 O2(g) ---> 8 SO2(g)

Write the balanced equation that shows the synthesis reaction between potassium metal & fluorine gas:potassium + fluorine ---> potassium fluoride2 K(s) + F2(g) ---> 2 KF(s)

Write the balanced equation that shows the synthesis of reaction between iron & oxygen (remember iron has 2 possible oxidation states, 3+ & 2+):iron + oxygen ---> iron (III) oxide4 Fe(s) + 3 O2(g) ---> 2 Fe2O3(s)oriron + oxygen ---> iron (II) oxide2 Fe(s) + O2(g) ---> 2 FeO(s)

Write the balanced equation for the synthesis reaction between sulfur & oxygen (common oxide of sulfur is sulfur dioxide):sulfur + oxygen ---> sulfur dioxideS8(s) + 8 O2(g) ---> 8 SO2(g)

2) An element and a compound form a new compound2) An element and a compound form a new compound2) An element and a compound form a new compound

- products cannot be predicted with certainly- products formed during the reaction must be

collected and analyzed

- products cannot be predicted with certainly- products formed during the reaction must be

collected and analyzed

carbon monoxide + oxygen ---> carbon dioxide2 CO(g) + O2(g) ---> 2 CO2(g)

3) Two compounds form a new compound3) Two compounds form a new compound3) Two compounds form a new compound

a) non-metal oxide with water- forms an ACID

sulfur trioxide + water ---> sulfuric acidSO3(g) + H2O(l) ---> H2SO4(aq)

sulfur trioxide + water ---> sulfuric acidSO3(g) + H2O(l) ---> H2SO4(aq)

b) a metal oxide with water- forms a BASE

calcium oxide + water ---> calcium hydroxideCaO(s) + H2O(l) ---> Ca(OH)2(aq)

calcium oxide + water ---> calcium hydroxideCaO(s) + H2O(l) ---> Ca(OH)2(aq)

Learning Check:

1) Predict the product that is likely to form in each synthesis reaction. Then write a balanced chemical equation for the reaction.

a) silver & sulfur ---> ___________________________

! _______________________________________________________________

b) nickel & nitrogen ---> _________________________

! _______________________________________________________________

c) antimony & chlorine ---> _______________________

! _______________________________________________________________

d) hydrogen and sulfur ---> _______________________

! _______________________________________________________________

e) manganese & oxygen ---> ______________________

! _______________________________________________________________

f) aluminum & iodine ---> _________________________

! _______________________________________________________________

2) Determine if an acid of a base is formed when each oxide is placed in water. Be prepared to write the balanced equation for the formation of bases, as well as the following examples of acid formation.

a) carbon dioxide = ______________

! _______________________________________________________________

b) magnesium oxide = ____________

! _______________________________________________________________

c) sulfur trioxide = ________________

! _______________________________________________________________

d) potassium oxide = _____________

! _______________________________________________________________

Decomposition Reactions

A decomposition reaction involves one reactant compound breaking down into two or more products. Products can be any combination of elements and compounds:

- two different elements- an element and a compound- multiple compounds

The general form of a synthesis reaction is AB ---> A + B

Types of Decomposition Reactions:

Type of Reaction Examples

1) a binary compound decomposes into its elements

magnesium chloride ---> magnesium + chlorineMgCl2(s) ---> Mg(s) + Cl2(g)

2) a hydrate decomposes into an ionic compound and water

barium hydroxide octahydrate ---> barium hydroxide + waterBa(OH)2 * 8H2O(s) ---> Ba(OH)2(s) + 8H2O(g)

3) a metal nitrate decomposes into a metal nitrite & oxygen gas

potassium nitrate ---> potassium nitrite + oxygenKNO3(s) ---> KNO2(s) + O2(g)

4) a metal carbonate decomposes into a metal oxide & carbon dioxide gas

zinc carbonate ---> zinc oxide + carbon dioxideZnCO3(s) ---> ZnO(s) + CO2(g)

5) a metal hydroxide decomposes into a metal oxide & water

potassium hydroxide ---> potassium oxide + waterKOH(s) ---> K2O(s) + H2O(g)

Learning Check:

Determine the products that are likely to form in the decomposition of each compound. Then write a balanced chemical equation for the reaction.

a) sodium bromide ---> ___________________________________________________________

______________________________________________________________________________

b) aluminum sulfide ---> ___________________________________________________________

______________________________________________________________________________

c) titanium (III) hydroxide ---> ______________________________________________________

______________________________________________________________________________

d) potassium carbonate ---> _______________________________________________________

______________________________________________________________________________

e) iron (III) nitrate ---> ___________________________________________________________

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f) zinc chloride hexahydrate ---> ____________________________________________________

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g) nickel (II) nitrate ---> ___________________________________________________________

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h) magnesium carbonate ---> ______________________________________________________

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i) chromium (II) oxide ---> _________________________________________________________

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j) aluminum hydroxide ---> ________________________________________________________

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k) magnesium sulfate heptahydrate ---> ______________________________________________

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