1
Balancing act
Fill in the blanks from the word bank in the box below.
conserved
equal
same
subscripts
front
chemical formulae
written
1. During a chemical reaction, the mass of the reactants is the ___________ as the mass of the
products, or mass is ______________________.
2. A chemical equation is a ______________ representation of a chemical reaction with
________________ ______________________ (symbols).
3. The number of elements on the left side of a chemical equation needs to ____________ that
on the right side of the equation.
4. When balancing a chemical equation, never change the __________________ of the
chemical formulae. Instead, add numbers in ___________ of the chemical formulae to
balance the equation.
i.
Calcium (Ca) reacts with oxygen (O2) to produce calcium oxide (CaO)
Word equation:
Balanced
chemical equation:
Element tally:
ii.
Sodium metal (Na) reacts with chlorine molecule (Cl2) to produce sodium chloride (NaCl)
Word equation:
Balanced
chemical equation:
Element tally:
2
iii.
Magnesium (Mg) reacts with hydrochloric acid (HCl) to produce magnesium chloride (MgCl2)
and hydrogen molecule (H2)
Word equation:
Balanced
chemical equation:
Element tally:
iv.
Hydrogen molecule (H2) reacts with oxygen molecule (O2) to produce water (H2O)
Word equation:
Balanced
chemical equation:
Element tally:
v.
Nitrogen molecule (N2) reacts with hydrogen molecule (H2) to produce ammonia (NH3)
Word equation:
Balanced
chemical equation:
Element tally: