PHY S 100 Lesson 20

In order for a chemical reaction to occur

?

products

the end results of a chemical reaction

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.

reactants

the starting materials before a chemical reaction

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 decrease in the system?)

2H2 (gas) + O2 (gas) = 2 H2O (gas)

Which of the equations below is balanced correctly?

CH4 +2O2 ⇒ CO2 + 2H2O

Chemical bond rule

If the new molecular orbital is lower in an energy well and overall entropy increases, electrons go to this state and they can't get out—a chemical bond is formed. This chemical bond is stable unless energy is added.

anti-bonding orbital

The second type of orbital is called this because there is a low probability of electrons being between the two atoms

Energy and entropy are both involved in chemical reactions.

True

activation entropy

reactions will only take place when the reactants are lined up in a particular orientation.

A very fast reaction has a very high activation energy.

False

Molecular orbitals are the same shape as atomic orbitals.

False

How does a catalyst affect a reaction?

It lowers the activation energy.

bonding orbital

The first molecular orbital, a chemical bond can occur with this type of orbital and the electrons have a high probability of being between the two atoms

molecular orbitals

The orbital patterns which formed standing waves for a single nucleus do not form standing waves for this new situation.

These graphs 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?

graph goes up slightly but never returns all the way down to where the energy line is

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