Section 11.1 lecture for Honors & Prep Chemistry

1. Describing Chemical Reactions
On May 6, 1937, the huge airship Hindenburg
erupted into a fireball.
Within a short time, 210,000 cubic meters of
hydrogen had burned and the airship was
destroyed.
The chemical reaction that
occurred is
“hydrogen combines with
oxygen to produce water.”

2. Basic chemical equation format
Reactants Products
yields

3. Word Equations use chemical names
bleach + ammonia  poisonous gas

4. write the formulas of the reactants
to the left of the yields sign (arrow)
and the formulas of the products to
the right.
To write a chemical equation
H2 + O2  H2O
Reactants Product

5. An unbalanced(skeleton) equation
does not indicate the relative
amounts of the reactants and
products.
Here is the unbalanced equation
for rusting:
Fe + O2  Fe2O3 Why is it
unbalanced?

6. Methane + Oxygen  Carbon dioxide + Water
CH4 + O2  CO2 + H2O

7. A catalyst is a substance that
speeds up the reaction but is not
used up in the reaction.
Without Catalyst With Catalyst

8. Special conditions, including use
of a catalyst, are written above
the arrow
H2O2 H2O + O2
KI

9. Writing Chemical Equations

10. Complete chemical equations
show the state of matter
(in parenthesis) after each
formula.
NaCl (s )
H2O (l )
O2 (g )

11. iron + oxygen → iron(III) oxide
Fe(s) + O2(g)  Fe2O3(s)

12. Hydrogen Peroxide  Water and Oxygen
H2O2(aq)  H2O(l) + O2(g)

16. Chemical equations are not
complete unless they are
BALANCED.

17. To write a balanced equation add
the coefficients that will show the
reaction obeying the law of
conservation of mass.
PRODUCTSREACTANTS

18. Coefficients are small whole
numbers that are placed in front
of the formulas in an equation in
order to balance it.
subscripts coefficient
2H2 + O2  2H2O
NEVER change subscripts

19. subscriptscoefficients
NEVER change subscripts

20. In a balanced equation each side
of the equation has the same
number of atoms of each element
and mass is conserved.

30. 1. Propane gas reacts with oxygen to
produce water vapor and carbon
dioxide. Choose the correct word
equation for this reaction.
a. propane + carbon dioxide → water
+ oxygen
b. propane + oxygen + water →
carbon dioxide
c. propane + oxygen + water +
carbon dioxide
d. propane + oxygen → water +
carbon dioxide

31. 2. What coefficient for H2SO4 is required to
balance the following equation?
Ca3(PO4)2 + ____ H2SO4 → 3CaSO4 + 2H3PO4
a. 1
b. 2
c. 3
d. 4