Chemistry Heat Review Name ____________________________________ Date ___________________

Vocabulary

Heat: _____________________________________________________________________________________________

Temperature: ______________________________________________________________________________________

Enthalpy: __________________________________________________________________________________________

Calorimetry: _______________________________________________________________________________________

Activation energy: ___________________________________________________________________________________

Formulas Heat of phase change Heat for temperature increase Heat of reaction Endothermic/Exothermic

1.) When you touch a chemical reaction system and it feels COLD it means…… a.) heat is coming out of the system and into your hand c.) heat is coming into the system from your hand

b.) heat is not moving from one system to another d.) heat is being created from nothing

2.) When you touch a chemical reaction system and it feels WARM it means…… a.) heat is coming out of the system and into your hand c.) heat is coming into the system from your hand

b.) heat is not moving from one system to another d.) heat is being created from nothing

3.) When you touch a chemical reaction system and it feels WARM the reaction in that system is: (endothermic) or (exothermic), (circle one)? 4.) When you touch a chemical reaction system and it feels COLD the reaction in that system is: (endothermic) or (exothermic), (circle one)? 5.) When an endothermic reaction occurs the products will have than the reactants. a.) more energy b.) less energy c.) the same energy 6.) When an exothermic reaction occurs the products will have than the reactants. a.) more energy b.) less energy c.) the same energy 7.) Which statement best represents the relationship between endothermic and exothermic reactions AND the Law of Conservation of Energy? a.) energy is created by exothermic reactions b.) energy is destroyed by endothermic reactions c.) energy goes back and forth between systems by endothermic and exothermic reactions d.) cold systems illustrate how energy can disappear into nothing

Potential Energy Diagrams 1. Is the reaction exothermic or endothermic?

3. What is the value of the activation energy of the reaction? 4. What is the potential energy of the products? 5. What is the potential energy of the activated complex? Temperature-Heat Absorbed Graph and Calculations Draw the graph for the temperature versus heat graph for Ethanoic Acid. State what is happening in each of the lines of the graph and label the melting point at 14°C and the boiling point at 118°C 1) How much energy does it take to raise 12g of Ethanoic Acid to its melting point from 0 °C then melt it then raise it to

the boiling point? Heat of fusion is 192 . Heat of vaporization is 395 . Specific Heat is 2.04 °

Heat Calculations 1) The latent heat of vaporization of water is 2260 J/g. The molar heat of vaporization of water is 40.7 .How much

energy is released when 100 grams of water condenses from vapor at 100 °C? 2) How much energy will it take to melt 100 grams of ice at 0 °C? The latent heat of fusion of water is 334 J/g and the

molar heat of fusion for water is 6.01 3) Gold has a specific heat of 0.129 ° . How many joules of heat energy are required to raise the temperature of 15

grams of gold from 22°C to 85°C? 4) If the temperature of 34.4 g of ethanol increases from 25 °C to 78.8 °C, how much heat has been absorbed by the

ethanol? The specific heat of ethanol is 2.44 °

5) The overall reaction in commercial heat packs can be represented as 4Fe (s) + 3O2 (g) 2Fe2O3 (s) H = -1652 kJ

a) How much heat is released when 4.00 mol of iron is reacted with excess of O2?

b) How much heat is released when 1.00 mol Fe2O3 is produced?

c) How much heat is released when 1.00 g of iron is reacted with excess O2?

d) How much heat is released when 10.0 g O2 reacts?

a) Determine the Activation Energy for the forward

reaction... _______________kJ

b) Determine the Activation Energy for the reverse

reaction.... _______________kJ

or the forward

reaction?.. _______________kJ

reaction?.. _______________kJ

e) The forward reaction is _____________thermic.

f) The reverse reaction is ______________thermic.

The above graph shows the heat absorbed by 2 kg of an unknown substance. Notice that the heat is given in kilojoules, not joules.

1. Label the different regions of the graph as solid, liquid, gas, melting, and boiling.

2. What is the freezing point of the substance? (At what temperature does it freeze?)

3. What is the condensation point of the substance?

4. What is the melting point of the substance?

5. What is the boiling point for this substance?

6. Is the temperature changing during the liquid phase or staying constant?

7. What is the temperature change of the liquid phase?

8. Which line relates to fusion?

9. During which parts of the graph is the kinetic energy of the molecules constant?

1) The latent heat of vaporization of water is 2260 J/g. How many grams of water at 100°C can be converted to steam by 226,000 J of energy?

2) The latent heat of fusion of water is 334 J/g. How much energy is released when 20 grams of water at 0°C undergoes

freezing? 3) The latent heat of fusion of water is 334 J/g. How many grams of ice 0°C will melt by the addition of 3.34 kJ of heat

energy? 4) The latent heat of vaporization of water is 2260 J/g. How many kilojoules per gram is this? How many grams of

water will be vaporized by the addition of 2.260 x 103 J of heat energy at 100°C? 5) How many joules are needed to warm 25.5 grams of water from 14ºC to 22.5ºC?

6) Calculate the number of joules released when 75.0 grams of water are cooled from 100.0ºC to 27.5ºC. 7) If 1.13 x 104 J of heat is added to a water sample and the temperature rises from 88.0 ºC to its boiling point, what

mass of water is in the sample? 8) The specific heat capacity of gold is 0.128 J/g ºC. How much heat would be needed to warm 250.0 grams of gold

from 25.0 ºC to 100.0 ºC? 9) The specific heat capacity of zinc is 0.386 J/g ºC . How many joules would be released when 454 grams of zinc at 96.0

ºC were cooled to 28.0 ºC? 10) What is the temperature change if 1.386 x 103 J is absorbed by 60.0 g of copper which has a specific heat capacity of

0.385 J/g ºC?