Chapter 3: Mass Relationships in Chemical Reactions

Question 1

What is the definition of atomic mass?

Answer 1

the mass of an atom in atomic mass units (amu)

Question 2

What is the average atomic mass?

Answer 2

the weighted average of all of the naturally occurring isotopes of the element.

Question 3

What is Avogadro’s constant?

Answer 3

6.022 × 10^23

Question 4

What is the equation linking mass, moles and molecular mass?

Answer 4

Mass = moles x molecular mass

Question 5

What is formula mass?

Answer 5

the sum of the atomic masses (in amu) in a formula unit of an ionic compound.

Question 6

How do spectrometers work?

Answer 6

• Sample’s gaseous molecules collide with electrons to produce
positive ions.
• Positive ions (of mass m and charge e) are accelerated by two oppositely charged plates.
• Emerging ions are deflected into a circular path by a magnet.
• The radius of the path depends on the e/m (ions of smaller e/m ratio trace a wider curve than those having a larger e/m ratio).
• Ions with equal charges but different masses are separated from one another.
• The mass of each ion (and hence its parent atom or molecule) is determined from the magnitude of its deflection.
• Ions arrive at the detector (registers the current for each ion). The amount of current generated is directly proportional to the number of ions (determine the relative abundance of isotopes).

Question 7

Determine the empirical formula of a compound that has the following
percent composition by mass: K 24.75, Mn 34.77, O 40.51 percent.

Answer 7

KMnO4

Question 8

What is a chemical reaction?

Answer 8

A process in which one or more substance(s) is changed into one
or more new substance(s)

Question 9

What is the theoretical yield?

Answer 9

the amount of product that would result if all the limiting reagent reacted.

Question 10

What is the a actual yield?

Answer 10

the amount of product actually obtained from a reaction.