APPENDIX 7: SYMBOLS IN CHEMICAL EQUATIONS
Chemical formula: indicates the number of each atom in a substance.
Examples: H2(g) O2(g) H2O(l)
Chemical equation: indicates a chemical reaction with reactants and products.
Example: hydrogen(g) + oxygen(g) →
Symbol
Function
“produces” , “yields”, “gives” (“creates”)
To separate the reactants from the products. Never substitute with = signs.
“and”
To separate reactants from other reactants (or products from other products
Catalyzed* by iron (solid).
Information over the arrow indicates catalysis or solvent.
The reactant(s) is(are) heated.
Information over the arrow indicates catalysis or solvent.
The reaction (rxn) is catalyzed through electrolysis
(electricity).
Information over the arrow indicates catalysis or solvent.
The reaction undergoes photolysis (catalyzed with
light/radiation).
The term “h” (nu = frequency) represents the energy of a photon of light
The reaction occurs at 4°C.
Temperature over the arrow indicates rxn temperature.
The reaction occurs in alcohol.
Information over the arrow indicates catalysis or solvent.
(s)
“solid” (powder, crystals, ingot, precipitate, etc...)
Written as a subscript to indicate the state of a substance.

Old school: specifically indicates a precipitate (ppt)
Indicates a solid precipitate (product side only).
“liquid”
Written as a subscript to indicate the state of a substance
“gas” (gas, bubbles)
Written as a subscript to indicate the state of a substance.
Old school: specifically indicates a “gas” product.
Indicates a gas on the product side only, especially when the reactants are not
gases. Never seen on reactant side.
(aq)
“aqueous” (dissolved in water, solution)
Written as a subscript, indicates substance is dissolved in water.
NR
No reaction (no rxn)
Indicates no observable change in physical/chemical properties.
+
Fe(s)
→
→
water(l)
“Translation” into English
→
→
∆
∆
electrolysis
→
elec.
→
→
→
hν
4 °C
alcohol(l)
(l) or (l)
(g)

* “Catalysis” (for now) means “makes the reaction go faster.”
Examples:
OR
OR
OR
hydrochloric acid(aq)
+
sodium carbonate(s)

sodium chloride(aq)
+
carbon dioxide(g)
+
water(l)
aqueous hydrochloric acid
and
solid sodium carbonate
produce
aqueous sodium chloride
and
carbon dioxide gas
and
water
sodium phosphate(aq)
+
barium nitrate(aq)

sodium nitrate(aq)
+
barium phosphate(s)
aqueous sodium phosphate
and
aqueous barium nitrate
yield
aqueous sodium nitrate
and
solid barium phosphate
a solution of sodium phosphate
and
a solution of barium nitrate
yield
a solution of sodium nitrate
and
a barium phosphate precipitate
iron(II) chloride(aq)
+
sodium hydroxide(aq)

iron(II) hydroxide 
+
sodium chloride(aq)
aqueous iron(II) chloride
and
aqueous sodium hydroxide
yield
solid iron(II) hydroxide
and
aqueous sodium chloride
a solution of iron(II) chloride
and
a solution of sodium hydroxide
yield
an iron(II) hydroxide precipitate
and
a solution of sodium chloride
sulfuric acid(aq)
+
potassium(s)

potassium sulfate(aq)
+
hydrogen 
aqueous sulfuric acid
and
potassium solid
yield
aqueous potassium sulfate
and
hydrogen gas
a solution of sulfuric acid
and
potassium solid
yield
a solution of potassium sulfate
and
gaseous hydrogen
hν
water(l)
+
oxygen(g)
when catalyzed with light, produces
water
and
oxygen gas
hydrogen peroxide(l)
liquid hydrogen peroxide
→
elec.
potassium(s)
+
sulfur(s)
when catalyzed with electricity, produces
potassium metal (solid)
and
solid sulfur
potassium sulfide(s)
solid potassium sulfide
→
methane(g)
+
oxygen(g)
methane gas
and
oxygen gas
Δ
carbon dioxide(g)
+
water(g)
when heated, produce
carbon dioxide gas
and
water vapor
→