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CHM 1020 Exam 3 Study Guide/Practice Questions And Answers graded A+ by experts 2024/2025
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CHM 1020 Exam 3 Study Guide/PracticeQuestions And Answers
A calorie is defined as exactly 4.184 J. Therefore 1.000 Cal is exactly - ANS4184 J (Remember
that a Cal = 1000 cal or 1000kJ)
The heat energy released or absorbed by a chemical reaction is generally determined by the
difference between the energy that _______________ - ANSmust be put in to break the bonds
in the reactants and the energy that is released upon making the bonds in the products
(Remember that making bonds releases energy and breaking them requires energy input)
Oxygenated gasolines are blends of petroleum-derived compounds with oxygen-containing
compounds. Which of the following oxygenated compounds has been discontinued in some
states because of potential health risks? - ANSMTBE
The measure of how much energy is dispersed in a given process is called the - ANSentropy
T/F: the energy that is lost through entropy sometimes allows a system to be 100% efficient. -
ANSFALSE. This is the small amount of energy that is lost and *never allows any system to be
100% efficient.
Use the equation to help you calculate the heat of combustion of ethylene, C2H4. The bond
energies are: C H 416 kJ/mol; C C 356 kJ/mol; CC 598 kJ/mol; OO 498 kJ/mol; CO 803 kJ/mol;
H — O 467 kJ/mol.
The heat of combustion of ethylene is _________________ - ANS-1324 kJ/mol. (remember it's
reactants - products)
In which example is the entropy of the initial state lower than the entropy of the final state? -
ANSA pot of water boils to produce water vapor at 100 degrees C
Which of the following is not a step in fractional distillation of crude oil? - ANSFractions are
mixed with natural gas to enrich the hydrocarbon content (Remember that this process starts
with the whole oil fraction and separates it.)
The following molecules contain only single bonds.
NH3(g) + 3F2(g) → NF3(g) + 3 HF(g)
, The bond energies are: N — H 391 kJ/mol; F — F 158 kJ/mol; N — F 272 kJ/mol; H — F 566
kJ/mol. Which is the heat evolved or absorbed per mole of NH3 that reacts with F2? - ANS-867
kJ/mol (Remember - take the sum of all bonds formed minus all bonds broken aka reactants -
products)
Combustion is a chemical process in which a fuel combines with ________ to release energy
and form products. - ANSoxygen (Remember that this gas is considered a fuel for any
combustion)
The heat of combustion for the combustion of propane,
C3H8 + 5O2 ⟹ 3CO2 + 4H2O , is equal to -2,200 kJ.
This is an example of a(n) ____________ reaction. - ANSexothermic
Given the following reaction what is the energy of this reaction:
N2 + O2 ⟹ 2NO?
Use the following bond energies N≡N = 946 kJ/mol, O=O = 498 kJ/mol; N=O = 607 kJ/mol -
ANS+230 kJ (endothermic)
Which law of thermodynamics states that the entropy, or randomness, of the universe is
increasing? - ANSsecond
As alakanes (hydrocarbons) become larger/longer (more carbons) the boiling point
_____________. - ANSincreases
A(n) ________________ is a molecule with the same formula but different chemical structure. -
ANSisomer
renewable fuels derived from biological sources - ANSbiofuel
the energy necessary to initiate a chemical reaction - ANSactivation energy
the tendency for atoms to give/take or share electrons to get eight valence electrons - ANSoctet
rule
A process of separating out various compounds by heating them to their boiling points,
collecting the vapor and condensing it - ANSdistillation
decaying plant life from millions of years ago - ANSfossil fuels
List examples of exothermic processes: (4) - ANS1. a mammal metabolizing food
2. the reaction in a chemical "hot pack" for warming hands in winter
3. burning candle
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