Name: ________________________
Hour: ____ Date: ___________
Chemistry: Heat Energy Problems
Solve each of the following problems. Show work and include units to earn full credit. You will need to use a
reference source to find the specific heat capacity of each substance.
1. 200 g of water at 30oC are mixed with 20 g of silver at 350oC. Find the final temperature of the system.
qlost , Ag

[ Cp, Ag
qgain, water
 m 
t ]  Cp, water
 m 
t
-[ (0.235J / g  oC )(20 g )( X oC - 35o C )]  (4.184J / g  oC )(200 g )( X oC - 30o C )
[4.7 X  1645]  836.8 X  25.1
1645 - 4.7 X  836.8 X - 25104
26749  841.5 X
X
 31.8 oC
2. 26 g of water at 18oC are mixed with 49 g of water at 70oC. Find the final temperature of the system.
qlost , water

[ Cp, water
qgain, water
 m 
t ]  Cp, water
 m 
t
-[ (4.184J / g  oC )(49 g )( X oC - 70o C )]  (4.184J / g  oC )(26 g )( X oC - 18 o C )
[205 X  14351]  108.8 X  1958
14351 - 205 X  109 X - 1958
16309  314 X
X
 51.9 oC
3. 84 g of water at 22oC are mixed with 150 g of ethanol at 88oC. Find the final temperature of the system.
qlost , ethanol
[ Cp, ethanol

qgain, water
 m 
t ]  Cp, water
 m 
t
-[ (2.438J / g  oC )(150 g )( X oC - 88o C )]  (4.184J / g  oC )(84 g )( X oC - 22o C )
[365.7 X  32182]  351.4 X  7732
32182 - 365.7 X  351.4 X - 7732
39914  717.1X
X
 55.7 oC
4. 24 g of sodium chloride at 25oC are mixed with 272 g mercury at 50oC. Find the system’s final temperature.
qlost , Hg

[ Cp, Hg
qgain, NaCl
 m 
t ]  Cp, NaCl
 m 
t
-[ (0.139J / g  oC )(272 g )( X oC - 50o C )]  (0.865J / g  oC )(24 g )( X oC - 25 o C )
[37.8 X  1890.4]  20.8 X  519
1890.4 - 37.8 X  20.8 X - 519
2409.4  58.6 X
 41.1oC
X
5. 240 g of water at 20oC are mixed with a sample of iron at 500oC. The final temperature of the system is
42oC. Find the mass of the iron sample.
qlost , Fe

[ Cp, Fe
qgain, water
 m 
t ]  Cp, water
 m 
t
-[ (0.449J / g  oC )( X g )(42o C - 500o C )]  (4.184J / g  oC )(240 g )(42o C - 20o C )
205.6 X  22902
X
 107.4 g Fe
6. 75.0 g of water at 30oC are mixed with 83.8 g of a solid metal at 600oC. The final temperature of the system
is 50oC. What is the metal?
qlost , ? metal

[ Cp, ? metal
qgain, water
 m 
t ]  Cp, water
 m 
t
-[ (Cp, ? metal )(83.8 g )(50o C - 600o C )]  (4.184J / g  oC )(75 g )(50 o C - 30 o C )
46090(Cp, ? metal )  6276
Cp, ? metal
 0.136 J / g  oC
From table :
Cp, Hg
 0.139 J / g  oC
C p, W
 0.132 J / g  oC
* Mercury is liquid at room temperature : tungsten is solid at 600o C.
7. A 135 g sample of aluminum at 400oC is placed in water at 25oC. The final temperature of the system is
80oC. Find the mass of the water.
qlost , Al

[ Cp, Fe
qgain, water
 m 
t ]  Cp, water
 m 
t
-[ (0.897J / g  oC )(135 g )(80o C - 400o C )]  (4.184J / g  oC )( X g )(80o C - 25o C )
38750  230 ( X g )
X
Answers:
 168.5 g H2O
1.
2.
3.
31.8oC
52.0oC
55.7oC
4.
5.
6.
41.1oC
107.3 g Fe
tungsten
7.
168.6 g H2O
Name: ________________________
Hour: ____ Date:
___________
Chemistry: Heat Energy Problems
Solve each of the following problems. Show work and include units to earn full credit. You will need to use a
reference source to find the specific heat capacity of each substance.
1. 200 g of water at 30oC are mixed with 20 g of silver at 350oC. Find the final temperature of the system.
2. 26 g of water at 18oC are mixed with 49 g of water at 70oC. Find the final temperature of the system.
3. 84 g of water at 22oC are mixed with 150 g of ethanol at 88oC. Find the final temperature of the system.
4. 24 g of sodium chloride at 25oC are mixed with 272 g mercury at 50oC. Find the system’s final temperature.
5. 240 g of water at 20oC are mixed with a sample of iron at 500oC. The final temperature of the system is
42oC. Find the mass of the iron sample.
6. 75.0 g of water at 30oC are mixed with 83.8 g of a solid metal at 600oC. The final temperature of the system
is 50oC. What is the metal?
7. A 135 g sample of aluminum at 400oC is placed in water at 25oC. The final temperature of the system is
80oC. Find the mass of the water.
Answers:
1.
2.
3.
31.8oC
52.0oC
55.7oC
4.
5.
6.
41.1oC
107.3 g Fe
tungsten
7.
168.6 g H2O