AP Chem practice test

In which of the following processes will ∆S° be negative?

Of the three solutions listed in the table above, which one, if any, has the greatest electrical conductivity and why? 

• 0.1 M HC2H3O2(aq)  because its molecules have the most atoms.

• 0.1 M KI(aq)  because KI completely dissociates in water to produce ions.

• 0.1 M CH3OH(aq)  because its molecules can form hydrogen bonds.

• All three solutions have the same electrical conductivity because the concentrations are the same.

Tags

NGSS.HS-PS2-5

H2(g) + I2(g) ↔  2 HI(g)

Hydrogen gas reacts with iodine gas at constant temperature in a sealed rigid container. The gases are allowed to reach equilibrium according to  the equation above. Which of the following  best describes what will happen to the reaction immediately after additional iodine gas is added to the system? 

• The rates of both the forward and reverse reactions decrease.

• The rates of both the forward and reverse reactions do not change.

• The rate of the forward reaction becomes greater than the rate of the reverse reaction.

• The rate of the forward reaction becomes less than the rate of the reverse reaction.

Tags

NGSS.HS-PS1-5

The first five ionization energies of an unknown element are listed in the table above. Which of  the following statements correctly identifies the element and cites the evidence supporting the identification?

• Na, because of the large difference between the first and the second ionization energies

• Al, because of the large difference between the third and fourth ionization energies

• Si, because the fifth ionization energy has the greatest value

• P, because a neutral atom of P has five valence electrons

Tags

NGSS.HS-PS1-1

NGSS.HS-PS1-2

The diagram above represents a particle in aqueous solution. Which of the following statements about the particle is correct? 

• The particle must be a cation because the negative end of each water molecule is pointed toward it.

• The particle must be an anion because the positive end of each water molecule is pointed toward it. 

• The charge of the particle cannot be determined because water molecules  have no net charge.

• The charge of the particle cannot be determined because the water molecules are arranged symmetrically and their partial charges cancel. 

Tags

NGSS.HS-PS1-3

A student obtains a mixture of the liquids hexane and octane, which are miscible in all proportions. Which of the following techniques would be best for separating the two components of the mixture, and why?

• Filtration, because the different densities of the liquids would allow one to pass through the filter paper while the other would not. 

• Paper chromatography, because the liquids would move along the stationary phase at different rates owing to the difference in polarity of their molecules. 

• Column chromatography, because the higher molar mass of octane would cause it to move down   the column faster than hexane. 

•  Distillation, because the liquids would boil  at different temperatures owing to the difference in strength of their intermolecular forces. 

Tags

NGSS.HS-PS1-6

To catalyze a biochemical reaction, an enzyme typically

• drives the reaction to completion by consuming byproducts of the reaction

• binds temporarily to reactant molecules to lower the activation energy of the reaction

• dissociates into additional reactant molecules, thereby increasing the reaction rate

• decomposes and releases energy to increase the number of successful collisions between reactant molecules 

Tags

NGSS.HS-PS1-5

Of the following diagrams, which best represents the structure of solid KF ?

• 
• 
• 
• 

Tags

NGSS.HS-PS1-3

*Look at your information on the packet.

Which of the following is the net ionic equation for the overall reaction that occurs as the cell operates?

• Ag(s) + Zn2+(aq)  → Ag2+(aq) + Zn(s)

• Ag+(aq) + Zn2+(aq) + 3 e −  → AgZn(s)

• Ag+(aq) + Zn(s) → Ag(s) + Zn2+(aq) + e −

• 2 Ag+(aq) + Zn(s) →  2 Ag(s) + Zn2+(aq)

Tags

NGSS.HS-PS1-7