Question

1. An 78.5 g piece of metal whose T = 63.00 ^oC is placed in a coffee cup calorimeter containing 125 g water.    When the system reaches equilibrium, the water has changed from 20.00 ^oC to 24.00 ^oC. What is specific heat of metal?
2. An 88.5 g piece of metal whose T = 78.8 ^oC is placed in a coffee cup calorimeter containing 244 g water.    When the system reaches equilibrium, the water has changed from 18.80 ^oC to 200 ^oC. What is specific heat of metal?
3. A piece of metal with specific heat 0.200 J/g ^oC is placed in a coffee cup calorimeter containing 296 g water at 25.00 ^oC. The temperature of the water rises to 31.20 ^oC. How much heat in kJ was lost by the metal? Watch units! Specific heat of water is 4.184 J/g ^oC  
4. 345.0 g of H ₂O at 62.0 ^oC cools to 26.0 ^oC.
   How many kJ of heat did it lose to the environment?
   The specific heat, c, of water is 184 J/g·C.
5. A metal object at 91.0 ^oC cools to 20 ^oC by losing 56 kJ of heat
   to the environment.
   What is the heat capacity, C, of the metal object in units of J/ ^oC?
6. An object at 40.0 ^oC is heated to 115.0 ^oC.
   How many kJ of heat did it gain from the environment?
   The heat capacity, C, of the object is 0.690 kJ/ ^oC.
7. 200.0 g of H ₂O at 44.0 ^oC lost 15.7 kJ of heat to a cooler environment.  
   What is its new temperature?
8. 200.0 g of H ₂O at 50.00 ^oC cools to 26.00 ^oC.
   How many kJ of heat did it lose to the environment? (Report the absolute value)
   The specific heat, c, of water is 4.184 J/g·C.
9. A metal object at 54.0 ^oC is heated by gaining 30.2 kJ of heat
   from the environment.
   The heat capacity, C, of the metal object is 6.30 kJ/ ^oC
10. When 11.53 g C₂H₆O (g) is reacted according to the following equation, 362.8 kJ of heat is released.   What is the ΔH of the reaction?
    C₂H₆O (g)            +   3O₂(g)        -->     2CO₂(g)   +   3H₂O (l)
11. When 2.45 g of CH₃OCH₃ is burned at constant Pressure, 77.42 kJ of heat is given off. What is ∆H for this reaction? Hint: watch sign!
      
    CH₃OCH₃(l) + 3O₂(g) -->    2CO₃(s)    + 3H₂O (g)    ∆ H _rxn = ?
12. SiO₂(s) + 3C (graphite) --> SiC (s) + 2CO (g)      ΔH _rxn =   624.6 kJ / mol rxn.
    Using the following standard enthalpy of formation data, calculate the standard enthalpy of formation for SiC (s).
    standard enthalpy of formation SiO₂(s)   =     -910.9 kJ/mol
    standard enthalpy of formation CO (g) =  -110.5 kJ/mol
13. 2C₈H₁₈   + 25O₂ → 16CO₂ + 18H₂O      
    ΔH° rxn = -11020 kJ/mol rxn
    Look at above equation. How many kJ of heat will be released when 7.00 grams of C₈H₁₈  is combusted?
14. Which of the following would be endothermic ?

		2Na + Cl2    ---> 2NaCl
		CH4 + 2O2 --> CO2 + 2H2O
		changing a solid iron nail to molten iron by melting it
		an iron nail rusts
		paper burns

15. The sign of ∆H for the process NaCl( s) --> NaCl( l) is
16. When 1.0 mole of ZnO changes into pure Zinc and oxygen, the ΔH = 348 kJ. What does this tell you about the reaction?
17. When pure hydrogen and fluorine change into HF, the reaction releases heat. What does this tell you about the reaction?
18. he sign of ∆H for the process Fe( s)     Fe( l) is (hint--what do you have to do to melt iron?

Answer 1

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