Download Balancing Chemical Equations

WS 3 Writing Balanced Chemical Equations (Part 2)
General guidelines for states of matter. Water is liquid (l) unless stated otherwise. Likewise,
compounds identified as alcohols are liquids unless otherwise stated. All acids are aqueous (aq).
Anything identified as a precipitate is a solid (s). Anything dissolved in water is aqueous. Of the
diatomic molecules, H2, O2, N2, F2, Cl2 are gases; Br2 is a liquid, and I2 is a solid. Noble gases are
always gaseous. Other nonmetal elements are solids unless otherwise stated. Most ionic compounds
and non-ionic compounds are solids unless otherwise stated. Simple hydrocarbon compounds like
methane, ethane and propane are gases. Other flammable hydrocarbons, such as butane, pentane,
hexane, heptane, and octane are liquids unless otherwise stated. Metals are always solids (except for
pure mercury, which is a liquid). Show pure metals and nonmetals (except for the diatomic molecules)
as single atoms in chemical equations unless otherwise noted.
11. When exposed to air, solid calcium sulfite reacts slowly with oxygen to form solid calcium sulfate.
2CaSO3(s)
+
O2(g)
 2CaSO4(s)
12. When heated, solid mercury(II) oxide decomposes to form mercury and oxygen. Through this
reaction, Joseph Priestley demonstrated the existence of oxygen in 1774.
2HgO(s)

2Hg(l)
+ O2(g)
13. Methanol, CH3OH, decomposes to form carbon monoxide and hydrogen gas.
CH3OH(l)

CO(g)
+ 2H2(g)
14. Potassium nitrate decomposes to form potassium nitrite and oxygen gas.
2KNO3(s)

2KNO2(s)
+
O2(g)
15. Aqueous antimony(V) chloride reacts with aqueous potassium iodide to form aqueous potassium
chloride, iodine crystals, and aqueous antimony(III) chloride.
SbCl5(aq)
+ 2KI(aq)

2KCl(aq)
+ I2(s)
+ SbCl3(aq)
16. Nitric acid reacts with hydrogen sulfide gas to form nitrogen dioxide gas, water, and sulfur.
2HNO3(aq)
+
H2S(g)

2NO2(g)
+
2H2O(l)
+
S(s)
17. Chromium(III) oxide reacts with silicon to form chromium metal and silicon dioxide.
2Cr2O3(s)

+ 3Si(s)
4Cr(s)
+ 3SiO2(s)
18. Ammonium dichromate, (NH4)2Cr2O7, decomposes to form chromium(III) oxide, nitrogen gas and
water.
(NH4)2Cr2O7(s)

Cr2O3(s)
+
N2(g)
+ 4H2O(l)
19. Iron(II) chloride reacts with water at high temperatures to form Fe3O4, hydrochloric acid, and
hydrogen gas.
3FeCl2(s)
+ 4H2O(l)

Fe3O4(s)
+ 6HCl(aq)
+
H2(g)
20. Aqueous aluminum sulfate reacts with aqueous calcium hydroxide to form aluminum hydroxide as a
precipitate and aqueous calcium sulfate.
Al2(SO4)3(aq)
+ 3Ca(OH)2(aq)
 2Al(OH)3(s) + 3CaSO4(aq)