Types of Chemical Reactions

Steps to Writing Reactions

• Some steps for doing reactions1. Identify the type of reaction

2. Predict the product(s) using the type of reaction as a model

3. Balance it

Br2 I2 N2 Cl2

H2 O2 F2

memorize these

Watch These Reactions!

Combination ( or Synthesis) Reactions• a chemical change in which two or more

substances react to form a single new substance

• the general form is A + X AX– 2Cu(s) + S(s) Cu2S(s)

– 2Fe(s) + 3S(s) Fe2S3(s)

– K(s) + Cl2(g) ?

• ions are: K+1 and Cl-1

• therefore: K(s) + Cl2(g) KCl(s)

• balanced: 2K(s) + Cl2(g) 2KCl(s)

Practice• Predict the products. Write the following

synthesis reaction equations.• Sodium metal reacts with chlorine gas

Na + Cl2 NaCl

• Solid Magnesium reacts with fluorine gas

Mg + F2 MgF2

• Aluminum metal reacts with fluorine gas

Al + F2 AlF3

• Now balance….

Decomposition Reactions• a chemical change in which a single

compound breaks down into two or more simple products.

• the general form is AX A + X– 2HgO(s) → 2Hg(l) + O2(g)

– Zn(ClO3)2 ZnCl2 + 3O2

– H2O(l) → ?

• H2O(l) → H2(g) + O2(g)

• 2H2O(l) → 2H2(g) + O2(g)

electricity

electricity

electricity

Practice

• Predict the products. Then, write and balance the following decomposition reaction equations:

• Solid Lead (IV) oxide decomposes– Pb is 4+ and O is 2- therefore…

• PbO2 Pb + O2

• Aluminum nitride decomposes– Al is 3+ and N is 3- therefore…

• AlN Al + N2

• May want to stop here

Single Replacement Reactions

• a chemical change in which one element replaces a second element in a compound

– metal+ will replace a metal +, or a nonmetal

- will replace a nonmetal -

– general form is A + BX B + AX

– zinc metal reacts with aqueous hydrochloric acid

– Zn (s) + 2HCl (aq) ZnCl2 (aq) + H2 (g)

– Ni + AgNO3 ?

• both Ni and Ag are positive ions

• see the activity series table to see which is the most reactive

–since nickel is… silver becomes free silver and the nickel becomes the nickel(II) ion (Ni+2) and will replace the silver

• NO3 is 1-

• Ni + AgNO3 Ag + Ni(NO3)2

–balance the equation:

–Ni + 2AgNO3 2Ag + Ni(NO3) 2

• aluminum metal reacts with aqueous copper (II) nitrate

– Al is a metal / Cu is 2+ and NO3 is 1-

– Al(s) + Cu(NO3)2(aq) ?

– Al is higher on the reactivity table and will replace Cu

– the new product is a result of the new Al 3+ and NO3 1- ions bonding

– Al(s) + Cu(NO3)2(aq) Cu(s) + Al(NO3)3(s)

– 2Al(s) + 3Cu(NO3)2(aq) 3Cu(s) + 2Al(NO3)3(s)

• Al + Fe2O3 ?

– O is 2- and therefore Fe was 3+

– aluminum will replace iron(III)– iron(III) becomes simply Fe, and aluminum

metal becomes Al3+

– Al + Fe2O3 Fe + Al2O3

– 2Al + Fe2O3 2Fe + Al2O3

Another one, but not as good as the last one

Double Replacement Reactions

• an exchange of positive ions between two chemicals– a reaction will occur if any of the new

products are any of the following:• a gas• water• a precipitate (see solubility table/cheat sheet)

• general form is AX + BY BX + AY

• CuSO4 + Na2CO3 Na2SO4 + CuCO3

• NaOH + CuSO4 ?

– look at the table to see if either new product will form a precipitate– if so, this indicates a reaction will take place

– yes, copper (Cu) and hydroxide (OH) will form a precipitate according to the table

• therefore, the Na+ and Cu2+ will switch places

• Na+ combines with SO42- to form Na2SO4.

• Cu2+ combines with OH- to form Cu(OH)2

• NaOH + CuSO4 Na2SO4 + Cu(OH)2

• 2NaOH + CuSO4 Na2SO4 + Cu(OH)2

• Assume the following double replacement reaction will take place:– Na2CO3 + HCl ?

– Na+1 combines with Cl-1 to form NaCl

– H+ combines with CO32- to form H2CO3

– Na2CO3 + 2HCl 2NaCl + H2CO3

– word equation?

Combustion Reaction

• a type of combination reaction where a substance reacts with oxygen

• often the burning of a fuel that produces carbon dioxide, water, light, and heat

• CH4 + O2 ?

• CH4 + O2 CO2 + H2O

• CH4 + 2O2 CO2 + 2H2O

Practice• Which type of reaction are the following?

• H2 + Cl2 2HCl

– combination

• Ca + 2H2O Ca(OH)2 + H2

– single replacement

Practice

• 2CO + O2 2CO2

– combination

• 2KClO3 2KCl + 3O2

– decomposition

Practice

• FeS + 2HCl FeCl2 + H2S

– double replacement

• Zn + HCl ?– single replacement

– Zn + 2HCl ZnCl2 + H2