Calculating
Reaction Energy Name
___________________
Balance
each of the following reactions, then calculate the amount of energy that is
absorbed or released in the reaction DH Rxn and
determine if the reaction is endothermic or exothermic
You
will be given a list of D Hf values on a separate sheet.
Balance first, then multiply the heat of formation for each
substance by the number of moles in the balanced equation
1. ___2_Na (s) +
___2_ H2O (l ) ® __2__NaOH
(aq) +
____H2(g)
(2 ´ 0) + (2 ´ -286) (2
´ -470) + (1 ´ 0 )
0 + - 572
® -940
+ 0
- 572 ® -940
D Hf = -940 + 572 = -368 (negative sign indicates exothermic)
In order to form the products, you have to break apart the
reactants, this means adding 572 kJ to the reaction, and then
940 kJ of energy will be released as the products form, so the net
result is a release of 368 kJ
DHRxn ___ -368 ________ Is the reaction endothermic or -368? _____ exothermic
________
2. ____AgNO3 (aq)
+ ____Pb (s) ®
____Pb(NO3)2
(aq) + ____ Ag (s)
DH Rxn ___________ Is
the reaction endothermic or exothermic?
_____________
3. ____Cu (s)
+ ____ Zn(NO3)2 (aq)
® ____Cu(NO3)2 (aq)
+ ____Zn (s)
DH Rxn ___________ Is
the reaction endothermic or exothermic?
_____________
4. ____ Zn
(s) ____HCl (aq)
® ____ZnCl2 (aq)
+ ____H2 (g)
DH Rxn ___________ Is
the reaction endothermic or exothermic? _____________
5.
____H2O (l ) + ____ CO2 (g) ® ____C12H22O11 (aq)
+ ____ O2 (g)
DH Rxn ___________ Is
the reaction endothermic or exothermic?
_____________
6. Al (s) + 3 I2 (g) ® 2 AlI3 (s)
DH Rxn ___________ Is
the reaction endothermic or exothermic?
_____________
7. ____Fe
(s) + ____Al2O3 (s)
® ____Al
(s) + ____Fe2O3 (s)
DH Rxn ___________ Is
the reaction endothermic or exothermic?
_____________
8. ____Mg
(s) + ____CO2 (g)
® ____MgO (s) + ____ C
(s)
DH Rxn ___________ Is
the reaction endothermic or exothermic?
_____________
9. ____ H2O2 (aq)
® ____ H2O (l
) + ____O2 (g)
DH Rxn ___________ Is
the reaction endothermic or exothermic?
_____________
10. ____ C8H18 (l ) +
____ O2 (g) ® ____ CO2 (g)
+ ____H2O (l )
DH Rxn ___________ Is
the reaction endothermic or exothermic?
_____________
11. ____KNO3 (aq)
+ ____Cu (s)
® ____ Cu(NO3)2 (aq)
____K (s)
DH Rxn ___________ Is
the reaction endothermic or exothermic?
_____________
12.
(detonation of Nitroglycerine)
4C3H5N3O9 (l ) ® 6N2 (g) +
12CO2 (g) +
10 H2O (l ) +
O2 (g)
DH Rxn ___________ Is
the reaction endothermic or exothermic? _____________
13. ____ CaCO3 (s)
+ ____HCl (aq) ®____CaCl2 (aq)
+ ____H2O (l )
+ ____CO2 (g)
DH Rxn
___________ Is the reaction
endothermic or exothermic? _____________
Heat or reaction values:
-15
-154
-190
-214
+218
-368
+568
-606
-809
+833
+5641
-6096
-11,018