Name:
POSWif \Zel
Date:
Period:
WS 9„.6:
Energy Stoichiomety
Directions: solve the following problems. Some of the problems will have to be balanced first.
1) How many kJ of energy will be released when 4.72 g of carbon react with excess oxygen gas to produce carbon
dioxide?
AH° = —393.5 kJ
C+ 02 4 CO2
C
tY\(C..-343.517.:5
2) How much energy should be transferred when 38.2 g of liquid bromine reacts with excess hydrogen gas to form
hydrogen bromide? Is the heat being transferred from the system to the surroundings or from the surroundings
to the system?
H2 + Br2 -› Z HBr
-36 /2-
5 21r2-
fclo Voci,
is1.6 3 91-2.
\
AH° = 72.80 kJ
12.43 tz-5
I mo1 gel
3) How many kJ of energy would you expect to be transferred when 6.44 g of sulfur react with excess oxygen gas to
produce sulfur trioxide? Is this reaction endothermic or exothermic?
ZS+
3O2 4 2. SO3
5 S k_ I cook S
AH° = —791.4 kJ
\-- -1c10-112:3 \
‘ 32.1 ) S \ 2 no1 s
x o-VAnec en ic
4) Nitrogen gas and oxygen gas can combine to produce nitric oxide, NO. If such a reaction absorbs 88.0 kJ of
energy from the surroundings, how many grams of nitrogen gas do you predict were consumed in the reaction?
N2+ 02 4 2.N0
8.0 kz-5
rnol
k 186
2.8 g
(1-101
AH° = 180 kJ
ft*
6) Ammonia gas combines with excess oxygen gas to produce nitric oxide and water. If 256 kJ of energy were
released in such a reaction, how many grams of ammonia gas were reacted?
4 NH3 + 502 4 4N0 + 6H20
AH° = — 1170 kJ
7) Carbon in the form of graphite combines with excess hydrogen gas to form benzene, C6H6. In the following
reaction 3.95 kJ of energy were transferred. Calculate the grams of graphite reacted. Is the reaction endothermic
or exothermic?
(o
C +3H2
C6H6
5. 'et
AH° = 49.03 kJ
C Cvoyht-\)
-en (icA4ne r(k.
8) How much energy will be released if 30.0 g of octane (C81118) is burned in excess oxygen?
2 C8H18 + IS 02 4 16 CO2 + (8 H20
AH = —10,966.8 kJ
-1,91-13
9) How much energy would be released by burning one gallon of octane? The density of octane is 0.703g/mL. 1
gallon = 3.79 liters.
— 12°0.60 k-5