Questions:
Topic / Objective: Reading chemical equations
Name:
Essential Question: How do we know if a chemical
equation abides by the law of conservation of mass?
Class:
Date:
Notes:
We use the molecular formula or empirical formula to determine how many elements exist
for a certain reaction shown in a chemical equation.
1. The molecular formula tells you the name and number of elements contained in a
compound.
We use molecular formula for covalent
compounds (compounds formed when two nonmetals react)
CH3CH2COOH is a covalent compound. It has
3 carbon atoms
6 hydrogen atoms
2 oxygen atoms.
Glucose has a molecular formula C6H12O6 contains;
6 carbon atoms
12 hydrogen atoms
6 oxygen atoms.
2. Empirical formula is used for ionic compounds, because an ionic compound consists
of repeating units.
Ionic compounds consist of a combination of a metal ion (cation) and a nonmetal
ion (anion)
e.g. NaCl consist of repeating units of;
1 sodium cation
1 chlorine anion
Be(OH)2 consists of repeating units of 1 beryllium cation, and 2 sets of (one oxygen
atom and one hydrogen atom)
Note that if symbols are in brackets, they are not ions.
Be(NO3)2 consists of repeating units of 1 beryllium cation, 2x (1 nitrogen atoms and 3
oxygen atoms)
Students are to use simulation ”Chemical molecular formulas”
http://www.physics-chemistry-interactive-flashanimation.com/chemistry_interactive/chemical_molecular_formulas_exercise.htm
-
In a chemical equation the total number of atoms in all reactants combined equals
the total number of atoms in all products combined
Word
Hydrogen(g)
+
Oxygen(g)  Water(g)
equation
Chemical
2H2(g)
+
O2(g)  2H2O(g)
equation
Total
4 Hydrogen + 2 Oxygen
4 Hydrogen + 2 Oxygen

= 6 atoms
= 6 atoms
atoms
Students are to use PhET simulation “balancing chemical equations”
https://phet.colorado.edu/sims/html/balancing-chemicalequations/latest/balancing-chemical-equations_en.html.
For each of the three reaction in the simulation students need to write the worded
equation, chemical equation and total atoms of reactants and products in their
Cornell notes.
On the right page students are to construct a one pager showing step-by-step
instructions on how to determine of an equation is balanced or not. They may use
the example of photosynthesis.
6CO2(g) + 6H2O(l) ----> C6H12O6(s) + 6O2(g)
EXTENSION:
Students are to research into the balanced chemical equations of the following:
-
The burning of petrol in a car engine
Mixing vinegar with bicarbonate soda
Burning gas in a Bunsen burner
Inserting magnesium metal in water.
Possible activities if students require more time for learning how to read a
chemical equation.
KAHOOTS:
https://create.kahoot.it/details/chemical-reactions-balancingequations/00511532-87e8-4037-ac55-27efb2769b37
https://create.kahoot.it/details/chemical-equations-and-reactions/c7da27d0449f-4444-8bac-9bb89dd6c959
Reading molecular formulas worksheet (attached)
Chemical equations worksheet (attached)
Chemical Equations
State whether each chemical equation is balanced or unbalanced?
Mg(s) + O2(g) ---> MgO(s)
2Na(s) + 2H2O(l) ---> 2NaOH(l) + H2(g)
NaCl(aq) + AgNO3(aq) ---> NaNO3(aq) + NaCl(s)
H2(g) + O2(g) ---> H2O(g)
CH3COOH(aq) + NaHCO3(s) ---> C2H3NaO2(aq) + CO2(g)
4Fe(s) + 3O2(g) + 6H2O(l) ---> 4Fe(OH)3(s)
6CO2(g) + 6H2O(l) ---> C6H12O6(s) + 6O2(g)
Reading chemical formulas
State each element in each compound. Also state how many of
each element it has.
Molecular Formulas of Covalent Empirical Formulas of Ionic
Compounds
Compounds
CH4
NaCl
H 2 O2
MgF2
CH3COOH
NaNO3
CH3CH3OH
NaOH
CH3C(OH)2CH3
Mg(OH)2
Mg(NO3)2
Write step by step instruction on how to identify what elements
exist in aluminium nitrate Al(NO3)3.