Vocab
Convert 234 calories to Joules (1 calorie= 4.184 J)
979 J
Predict the sign of entropy for the following process:
CO2(g) --> CO2(l)
entropy would be negative, system is becoming more ordered
Which conditions lead to a process that is spontaneous at all temperatures? (what would the sign for delta H and delta S be for this to be true?)
What is the difference between specific heat and heat capacity?
specific heat for a substance is the amount of energy required to heat 1 gram of a substance and raise its temperature by 1 degree Celsius; the heat capacity is more general and is the amount of heat required to raise the temperature of any mass of substance by 1 degree Celsius
What is the SI (system international) unit for energy?
Joule
How many joules of heat are lost by 3580 kg granite as it cools from 41.2oC to -12.9oC? (specific heat of granite is 0.790 J/g*oC)
1.56 x 108 J
Which state of matter has the largest entropy?
gas; most disorder
Could a reaction be spontaneous with a negative value for enthalpy and a negative value for entropy? How?
yes; if the temperature was low enough
a process that absorbs heat is called what?
endothermic; takes energy from the surroundings
This is the device used to measure the amount of energy released or absorbed during a chemical or physical process
calorimeter
How much heat is absorbed by a 2000 kg granite boulder as energy from the sun causes its temperature to change from 10 to 29oC (specific heat of granite is 0.790 J/g*oC)
30,000 kJ
Which of these two has a greater entropy?
NH3 (g) or NH3(aq)
NH3 (g)
Given enthalpy, entropy, and temperature data, calculate the ΔGsystem and determine whether the reaction is spontaneous or not.
ΔHsystem= 8.30 kJ, T= 273 K, ΔSsystem= -137 J/K
45,700 J
45.7 kJ
If you were to touch a flask inside of which an endothermic reaction was taking place, would it feel hot or cold? why?
cold- endothermic reactions absorb energy from their surroundings, in this case, your hand, making them feel cold to the touch
This is the heat content of a system at constant pressure
enthalpy
What mass of octane must be burned in order to liberate 5340 kJ of heat? delta Hcomb = -5471 kJ/mol
112g octane
Predict the sign of entropy for the reaction:
H2(g) + O2(g) --> 2H2O(l)
negative; two moles of gas yields one mole of liquid, gas has higher entropy
Could a reaction be spontaneous with a negative value for entropy and a positive value for enthalpy?
no- this will always be nonspontaneous (positive minus a negative will always be a positive number)
+-(-)= +
If heat is released by a chemical system, an equal amount of heat will be _____
absorbed by the surroundings; conservation of energy
In this type of chemical reaction or process, the energy stored in the chemical bonds of the reactants is greater than the energy stored in the bonds of the products
exothermic; releases extra energy to the surroundings
What is the final temperature of 1280 g of water originally at 20.0oC, if it absorbs 47.6 kJ of heat?
28.9oC
Predict the sign of entropy for the following reaction:
4FeS(s) + 7O2(g) --> 2Fe2O3(s) + 4SO2(g)
negative- more moles of gas on reactants side than products side
Given enthalpy, entropy, and temperature data, calculate the ΔGsystem and determine whether the reaction is spontaneous or not.
ΔHsystem= -456 kJ, T= 273 K, ΔSsystem= 1465 J/K
-856,000 J
-856 kJ
Determine delta H for the reaction of aluminum and sulfur dioxide:
4Al(s) + 3SO2(g) --> 2Al2O3(s) + 3S(s)
Use the following equations:
4Al(s) + 3O2(g) --> 2Al2O3(s) delta H = -3352 kJ/mol
S(s) + O2(g) --> SO2(g) delta H = -297 kJ/mol
-2461 kJ