#20 Write a balanced equation for the complete combustionof each compound:

a. formic acid: HCOOH

2HCOOH + O2 2 H2O + 2 CO2

b. heptane: C7H16

C7H16+ 11O2 8 H2O + 7CO2

21. Write a balanced equation for the complete combustion ofglucose: C6H12O6

C6H12O6 + O2 H2O + CO266 6

#22 What are the five types of chemical reactions?

#23 What are the keys to predicting the products of the fivegeneral types of reactions?

1. combination: Two elements combine to form one newcompound.

2. decomposition: one compound breaks up into its elements.

3. single replacement: one element replaces another in a compound.

4. double replacement: two compounds exchange ions to formtwo new compounds.

5. combustion: a fuel reacts with oxygen gas to form carbondioxide and water vapor.

#24 Classify each reaction and balance the equations:

a. C3H6 + O2 CO2 + H2O332 669

combustion

b. Al(OH)3 Al2O3 + H2O

decomposition

2 3

c. Li + O2 Li2O24

combination

d. Zn + AgNO3 Ag + Zn(NO3)22 2

single replacement

#25 Which of the five general types of reactions would mostlikely occur, given each set of reactants? What are the probableproducts?

a. an aqueous solution of two ionic compouds

double replacement is most likely. The most likely productsare two new compounds.

b. a single compound

a decomposition is most likely. The elements from which thiscompound is composed are the likely products.

c. two elementsa combination is most likely. The likely product will be a “combination” of the two elements

d. oxygen and a compound of carbon and hydrogencombustion. The likely products are CO2 and H2O

#26 complete and balance an equation for each reaction:

a. CaI2 + Hg(NO3)2 ? (HgI2 precipiates)

a. CaI2 + Hg(NO3)2 HgI2(s) + Ca(NO3)2

b. Al + Cl2 ?

c. Ag + HCl ?

d. C2H2 + O2 ?

e. MgCl2 ?

b. 2Al + 3Cl2 2AlCl3

c. 2Ag + 2HCl 2AgCl + H2(g)

d. 2C2H2 + 5O2 4CO2 + 2H2O

e. MgCl2 Mg + Cl2

#27 What are the three types of products that result in double-replacement reactions?