Chapter 4 Flashcards
What are atomic mass units abbreviated as?
amu
What is the mass of one carbon–12 atom in atomic mass units?
12 amu
1 AMU is equivalent to how many grams?
1.66 x 10–24 g
AMU is exactly 1/12 the mass of which type of atom?
carbon–12 atom
What does Atomic Mass Units (Amu) represent?
Average mass of all atoms of an element as it occurs in nature
Calculate the molar mass of citric acid (H3C6H5O7). What is the total?
192.1 g/mol
Calculation details: 8 H: 8 x 1.008 = 8.064; 6 C: 6 x 12.01 = 72.06; 7 O: 7 x 16.00 = 112.0
What is the formula mass of CaF2?
78.08 amu
Calculation: 1 Ca x 40.08 amu = 40.08 amu; 2 F x 19.00 amu = 38.00 amu
What is the formula mass of Ba(NO3)2?
261.3 amu
Calculation: 1 Ba x 137.3 amu = 137.3 amu; 2 N x 14.01 amu = 28.02 amu; 6 O x 16.00 amu = 96.00 amu
True or False: The atomic mass unit (amu) is a measure of the average mass of all isotopes of an element.
True
What does a molecular formula show?
Exact number of atoms of each element in a molecule
Example: C12H22O11
Define allotrope.
One of two or more distinct forms of an element
Examples include oxygen (O2) and ozone (O3), diamond and graphite (allotropic forms of carbon).
What does a structural formula illustrate?
General arrangement of atoms within a molecule.
What do empirical formulas reveal?
Elements present and their whole-number ratio in a compound.
What is the unit of measurement for atoms, molecules, ions, formula units, and particles?
Mole
The mole is a fundamental unit in chemistry used to count entities at the atomic or molecular scale.
What does Avogadro’s number represent?
The number of atoms in exactly 12 grams of carbon-12
Avogadro’s number is a key constant in chemistry and is approximately 6.02 x 10^23.
What is the value of 1 mole in terms of particles?
6.02 x 10^23
This number is used to convert between moles and the number of atoms, molecules, or other particles.
Fill in the blank: Avogadro’s number is our _______ number in chemistry.
counting
The concept of a counting number in chemistry is similar to using a dozen for counting items like cookies.
What are the three main pathway conversions in chemistry discussed?
Grams to Moles to Atoms
This conversion pathway is essential for stoichiometric calculations in chemical reactions.
How many atoms are found in 4.50 moles of silicon?
2.71 x 10^24 atoms
This is calculated using Avogadro’s number (6.022 x 10^23 atoms/mole) multiplied by 4.50 moles.
How many moles of silicon are in 2.45 x 10^45 atoms?
4.07 x 10^21 moles
This is calculated by dividing the number of atoms (2.45 x 10^45) by Avogadro’s number (6.022 x 10^23 atoms/mole).
What is a mole in chemistry?
A mole is a unit that measures the amount of substance, defined as exactly 6.022 x 10²³ particles (atoms, molecules, ions, etc.)
This number is known as Avogadro’s number.
How many moles are in 85.00 g of sodium chlorate (NaClO3)?
0.7988 mole
The molar mass of sodium chlorate is approximately 106.44 g/mol.
How do you calculate the number of grams in a given number of moles?
Multiply the number of moles by the molar mass of the substance
Formula: Grams = Moles x Molar Mass.
Determine the number of grams in 3.90 x 10–4 moles of magnesium fluoride (MgF2).
0.0380 grams
The molar mass of magnesium fluoride is approximately 62.30 g/mol.
How do you calculate the number of molecules from moles?
Multiply the number of moles by Avogadro’s number
Formula: Molecules = Moles x 6.022 x 10²³.
Determine the number of molecules in 4.6 moles of ethanol (CH3CH2OH).
2.77 x 10²⁴ molecules
Calculation: 4.6 moles x 6.022 x 10²³ molecules/mole.
