AP Chemistry : AP Chemistry
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Example Questions
Example Question #31 : Periodic Trends
Which atom has a smaller atomic radius than oxygen?
Sulfur
Lithium
Nitrogen
Fluorine
Fluorine
From left to right on the periodic table, atomic radius decreases because the number of protons increase while electrons are being added to the same shell; the attraction between the nucleus and the electron cloud override the shielding effect of adding electrons to the same shell. Therefore, those on the left are larger. From top to bottom on the periodic table, atomic radius/size increases because electrons are added to new valence shells significantly further from the nucleus than the previous shell. Therefore, those on the bottom left are largest. Sulfur is the largest since it is in period 3. The remaining atoms are in period 2, with lithium being the largest, followed by nitrogen, oxygen, and fluorine.
Example Question #31 : Periodic Trends
An atom in which of the following groups is most likely to lose an electron?
Alkali metals
Noble gases
Halogens
Alkaline earth metals
Alkali metals
The tendency to lose an electron is related to ionization energy, which is principally the opposite of electronegativity. The higher the ionization energy, the harder it is to pull an electron from the atom (takes more energy to ionize). Elements on the right side of the periodic table have higher ionization energies because they tend to gain electrons to achieve a full valence electron shell rather than lose them. Elements on the left side of the periodic table have lower ionization energies because they tend to lose electrons in their valence shell to achieve a full shell. Alkali metals need to lose 1 electron to achieve noble gas electron configuration, whereas the first electron lost from an alkaline earth metal does not confer this stability.
Example Question #171 : Ap Chemistry
Why are atomic halogens relatively reactive?
Halogens have an unpaired electron in their valence shell and they only need one more electron to obtain an octet
Halogens are monovalent anions, so they are very reactive
Gaseous halogens are very stable
None of the available answers
The valence shell of halogens has diradical character
Halogens have an unpaired electron in their valence shell and they only need one more electron to obtain an octet
Halogens have seven electrons in their valence shell, so they only need one more electron to obtain a completely filled valence shell. In addition, the unpaired electron in the seven electron shell is a radical which is highly reactive.
Example Question #1 : Special Groups
Which of the following is not a property of the noble gases?
Noble gases have low boiling points
Noble gases have low melting points
Noble gases have weak interatomic forces
All noble gases are monoatomic under standard conditions
Noble gases are stable because of their complete octet, so they cannot take place in any reaction
Noble gases are stable because of their complete octet, so they cannot take place in any reaction
While noble gases are very stable due to their filled octet, they actually do take place in certain reactions, so that is not a property of noble gases. All other answer choices are true.
Example Question #2 : Special Groups
Refer to Figure 1 for questions 1-6.
Below are the data for ionization energies of three elements X, Y, and Z. These elements are on the third peroid of the periodic table. The first four ionization energies for elements X, Y, and Z are given below in values of kJ/mol.
Figure 1: Ionization energies in kJ/mol for selected elements.
Which of the unknown elements would you expect to share chemical properties with strontium (Sr)?
Y and Z
Z
X and Y
X
Y
Z
We know that element Z is magnesium due to its jump bwtween ionization energies 2 and 3. Magnesium is in the second group of the periodic table and shares similar chemical properties with other alkali earth metals, such as strontium.
Example Question #3 : Special Groups
The periodic table of elements is organized in order of atomic number, whic describes how many protons are found in the atom's nucleus. The position of the element in the periodic table can also yield insight into how that atom will respond to other atoms and how it will participate in a chemical reaction.
Sodium is found in the alkali metal group on the periodic table. What type of ion would you expect sodium to form in order to achieve a stable octet?
A cation, with a charge of +1
A cation, with a neutral charge
An anion, with a charge of -1
An anion, with a charge of +1
A cation, with a charge of -1
A cation, with a charge of +1
Sodium is an alkali metal. All alkali metals are found in group 1 on the periodic table, and lose 1 electron in order to achieve a stable octet. Any ion that loses an electron, and thus becomes positively charged, is referred to as a cation. Anions are negatively charged ions, so sodium is not going to become an anion.
Example Question #3 : Special Groups
Below are the data for ionization energies of three elements X, Y, and Z. These elements are on the third peroid of the periodic table. The first four ionization energies for elements X, Y, and Z are given below in values of kJ/mol.
Figure 1: Ionization energies in kJ/mol for selected elements.
Which element(s) react(s) violently with water?
X and Y
X
Y and Z
Y
Z
X
We know element X is sodium due to its discrepancy between IE1 and IE2. Sodium has one valence electron and is an alkali metal. Pure alkali metals react violently with water. The heavier the metal, the bigger the explosion.
Example Question #1 : Laboratory Techniques And Analysis
3.2 g Zn and 8.1 g HCl are placed in an open beaker. As the reaction proceeds, the hydrogen gas is allowed to escape, causing the reaction to go to completion.
Which reactant (if either) is in excess, and how many grams of it remain?
Neither reactant is in excess.
First calculate the number of mols of each reactant:
The ratio of 
Now convert mols of 
Example Question #2 : Data Analysis And Other Calculations
25 mL of water at room temperature is vaporized and heated to 515 degrees Celsius in an open system.
What will the volume of the resulting gas be? Round your answer to the nearest liter.
The system is open, so the pressure can be assumed atmospheric, e.g. 1 atm.
Using the ideal gas law,
We need to convert 
The density of water at room temperature is approximately 1 g/mL, so we have 25 g of water. Convert to mols:
Plugging everything in:
Example Question #3 : Data Analysis And Other Calculations
A cylindrical metal wire, initially at 100 degrees Celsius, is immersed into a bomb calorimeter containing 100 mL of water at 25 degrees Celsius. After some time, the temperature of the system is homogenous at 35 degrees Celsius.
The wire is 135 cm long with a diameter of 0.1 cm.
What is the heat capacity of the metal? Round your answer to the nearest 
First we need to calculate the mass of the wire. We will do this by calculating its volume then multiplying by the density.
Next we need to find out how much energy the water gained from the metal wire.
The energy the water gained is equal to the energy the wire lost. This allows us to calculate the heat capacity for the metal:
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