It takes 1.25 kJ of energy to heat a certain sample of pure silver from 12.0C to 15.2C. The specific heat of silver is 0.24 J/gC. What is the mass of silver being heated?
1627.6 g
100
#1
-1376
200
When energy has a negative sign, is it moving into or out of the system?
Out of the system.
200
Lighting a match
Exothermic
200
Convert 5 Joules to calories. (4.184 Joules in 1 calorie)
1.20 Calories
200
Calculate the amount of energy required ( in joules) to heat 145 g of water from 22.3 to 75.0C. (specific heat of water is 4.184 J/gC)
31972 J
200
#2
-319.5
300
If work is being done on the system, would it be positive or negative?
Positive.
300
Getting a tan.
Endothermic
300
HCl + NaOH --> NaCl + H20 delta H = 500kJ/mol
Find delta H for 5 grams of NaOH in J
0.25 J
300
If 50 J of heat is applied to 10 g of iron, by how much will the temperature of the iron increase? The specific heat of iron is 0.45 J/gC.
11.1 C
300
#3
-818.3
400
Give and example of a state function & explain why it is a state function.
Elevation. No matter how you get there, the change is always the same. (Energy, Math problems, Enthalpy, Heat)
400
Using a cold pack.
Endothermic.
400
2.751 kJ into calories
657.5 calories
400
The specific heat capacity of gold is 0.13J/gC. Calculate the specific heat capacity of gold in cal/gC
0.03 cal/gC
400
#4
-604.1
500
If delta H is negative, is the reaction exothermic or endothermic?
exothermic.
500
Exercising.
Exothermic
500
Calculate delta E if the system gives off 50kJ of heat and has 50kJ of work done on it.
delta E = 0 kJ
500
Bonus Question: A 25.0 g sample of pure iron at 85C is dropped into 75 g of water at 20 C. What is the final temperature of the water-iron mixture. (s of iron is 0.45 J/gC)