PS 100 UNIT 3 CH 20
Which of the following equations is NOT balanced?
2Fe3O4 = 3Fe2O3 + O2
In order for a chemical reaction to occur:
Entropy must increase as a result of the reaction.
The graphs below show energy as a function of time for several different reactions. What does the height of the peak represent?
The activation energy
A temporary product of a chemical reaction that typically has more chemical potential energy than either the reactants or the final products. Equilibrium Activation energy Bonding orbital Transition state Antibonding orbital
Transition state
A reaction usually goes faster at higher temperatures.
True
An energetically favorable reaction gives off heat.
True
In the chemical equation C6H12O6 + 3O2= 3CO2 + 6H2O, how many oxygen atoms are on the right side of the equation?
12
In the equation C2H4 + 3O2 = ? CO2 + 2H2O, how many CO2 molecules are needed to balance the equation?
2
In which of the following processes is the end product more ordered than the reactants? (In which process does entropy decreases.)
2H2 (gas) + O2 (gas) = 2 H2O (gas)
The high energy orbital of the pair of MO's formed when two atomic orbitals combine.
Antibonding orbital
The low energy orbital of the pair of molecular orbitals (MO's) formed when two atomic orbitals combine.
Bonding orbital
Which of the equations below is balanced correctly?
CH4 +2O2 = CO2 + 2H2O
The point in a chemical reaction in which the forward and reverse reaction rates are equal.
Equilibrium
The energy that must be put into a system before a reaction can take place.
Activation energy
A very fast reaction has a very high activation energy.
False
in the upper atmosphere (also known as the ozone hole). As a catalyst, Cl may
be lowering the activation energy of some reaction involving ozone.
In a bonding orbital between two atoms, where is the electron density the highest? (Where do you have the highest probability of detecting an electron?)
In between the two atoms.
The graphs below show energy as a function of time for several different reactions. Which of the reactions shown below would release the most energy to the surroundings?
The reaction with the highest activation energy
The graphs below show energy as a function of time for several different reactions. Which of the reactions shown below would require the most energy to get started?
The reaction with the highest activation energy
The graphs below show energy as a function of time for several different reactions. Which of the reactions shown below would end up absorbing energy from the surroundings?
The reaction with the lowest activation energy
Electrons in a bonding molecular orbital are most likely to be found between the nuclei in a molecule.
True
Energy and entropy are both involved in chemical reactions.
True
A catalyst is a chemical that is present at the beginning of a reaction but not at the end.
False
Molecular orbitals are the same shape as atomic orbitals.
False
The probability waves (orbitals) that describe the possible locations for an electron in a molecule are exactly the same as those for an electron in an isolated atom.
False
How does a catalyst affect a reaction?
It lowers the activation energy
Which of the following is the best description of activation energy?
The energy that must be put into a system before a reaction can take place.
