AP Chemistry Section 1

A student has a 1g sample of each of the following compounds: NaCl, KBr, and KCl. Which of the following lists the samples in order of increasing number of moles in the sample?

• NaCl<KCl<KBr

• NaCl<KBr<KCl

• KCl<NaCl<KBr

• KBr<KCl<NaCl

A student obtains a sample of a pure solid compound. In addition to Avogadro’s number, which of the following must the student know in order to determine how many molecules are in the sample?

• Mass of the sample, volume of the sample

• Mass of the sample, density of the sample

• Molar mass of the compound, mass of the sample

• Molar mass of the compound, density of the sample

How many carbon atoms are contained in 2.8 g of C2H4 ?

• 1.2 x 10^23

• 3.0 x 10^23

• 6.0 x 10^23

• 1.2 x 10^24

• 6.0 x 10^24

In 1.00 mol of potassium zirconium sulfate trihydrate, K4Zr(SO4)4 • 3 H2O, there are

• 3 × 6.02 × 10^23 hydrogen atoms

• 6.02 × 10^23 sulfur atoms

• 4 × 6.02 × 10^23 potassium atoms

• 4 moles of oxygen atoms

The mass spectrum of the element Sb

is most likely represented by which of the following?

• 
• 
• 
• 

Which of the following elements has the mass spectrum represented above?

• Nb

• Mo

• U

• Cf

What is the empirical formula of an oxide of chromium that is 48 percent oxygen by mass?

• CrO

• CrO2

• CrO3

• Cr2O

When hafnium metal is heated in an atmosphere of chlorine gas, the product of the reaction is found to contain 62.2 percent Hf by mass and 37.4 percent Cl by mass. What is the empirical formula for this compound?

A compound contains 1.10 mol of K, 0.55 mol of Te, and 1.65 mol of O. What is the simplest formula of this compound?

• KTe2O

• K2TeO3

• K2TeO6

• K4TeO6

To gravimetrically analyze the silver content of a piece of jewelry made from an alloy of Ag and Cu, a student dissolves a small preweighed sample in HNO3(aq). Ag+(aq)and Cu2+(aq) ions form in the solution. Which of the following should be the next step in the analytical process?

• Centrifuging the solution to isolate the heavier ions

• Evaporating the solution to recover the dissolved nitrates

• Adding enough base solution to bring the pH up to 7.0

• Adding a solution containing an anion that forms an insoluble salt with only one of the metal ions