Chapter 1: 1.1 Atoms, Molecules, and Moles Flashcards
Atoms consist of:
Protons
Neutrons
Electrons
Charge of proton
Positive
Charge of neutron
Electrically neutral
Charge of electron
Negative
Do protons and neutrons have the same mass?
Almost the same mass
The mass of an electron is only ______th of the mass of a proton or a neutron
1/1836
Atomic number
The number of protons in an atomic nucleus
Where are protons and neutrons found?
In the atom’s nucleus
Mass number
The total number of protons and neutrons in an atom
Atomic mass unit
The chemical unit of atomic mass, also known as Dalton
Define 1 u (atomic mass unit)
Exactly 1/12 of the mass of a C-12 atom
What is Dalton denoted by?
“Da”
Isotopes
Atoms with the same number of protons but different numbers of neutrons
Isotopes have the same ____ number but a different ____ number
Same atomic number
Different mass number
Isotopic abundance
The percent by number of each of the isotopes of an element
Average atomic mass
The average of the masses of all of the isotopes of that element
Why is it that the atomic mass an element less than the atomic mass of the nucleus?
When protons and neutrons combine to form a nucleus, some of their total mass is converted into energy
What is the difference between the atomic mass of an element and the atomic mass of the nucleus known as?
Mass Defect
Neutral atom
Atoms that have an equal number of protons and electrons
Cation
Atom with a positive charge
Anion
Atom with a negative charge
What are ions of molecules called?
Molecular (or complex) ions
Compound
A molecule containing atoms of more than one element
Is O2 a compound?
No
Diatomic molecule
A molecule with only two atoms (such as O2)
Polyatomic molecule
A molecule with more than two atoms (such as H2O)
Empirical formula
Represents the simplest ratio of the numbers of atoms in a molecule
What is the empirical formula of glucose (C6H12O6)?
CH2O
Define a mole
The number of atoms contained in exactly 12 grams of pure carbon-12
What is the symbol for number of moles
n
Determine the number of individual atoms, molecules, or ions in a sample
Moles * Avogadro’s number
What is the number of atoms contained in exactly 12 grams of pure carbon-12 known as?
Avogadro’s number
(6.02 * 10^23)
1 mole of carbon-12 = __ grams
12 grams of carbon-12
If one mole of carbon-12 atoms has a mass of exactly 12 g, what is the mass in grams per mole for carbon-12?
12 grams per mole
Unit used for the mass of one atom
u
Unit used for the mass of a mole of atoms
g
Molecular mass
The mass of one molecule computed as the sum of atomic masses of all the atoms in the molecule
What is molecular mass usually expressed in?
Atomic mass units
Molar mass (MM)
The mass of one mole of molecules
What is the unit for molar mass?
Grams per mole
Formula of mass percent
(Mass of one species / Total mass of sample) * 100%
Mass percent of a species cannot exceed ____
Cannot exceed 100%
Sum of mass percents must add up to:
100%
Formula of mole fraction
(Number of moles of one species / Total number of moles)
Formula of Mole percent
Mole fraction * 100%
What is used to represent to mole fraction of an element or compound?
The symbol X with a subscript of the element or compound
Solution
A homogeneous mixture of two or more substances
Solute
Substance Dissolved
Solvent
Dissolving substance
Molarity
The number of moles of solute in one litre of the solution
Symbol for molarity
M
Formula for molarity
Amount of solute / Volume of solution
or
M = n/V
True or False:
When calculating molarity, volume can be calculated using millilitres or litres
False, when calculating molarity, volume can only be calculated using liters
Dilution
The process of reducing the concentration of a solution, either by adding the solvent or buy adding another solution
Provided no chemical reaction takes place, when a solution is diluted with the solvent, or mixed with a solution of another substance, does the number of moles of solute change?
No
Define a chemical reaction
A process in which one set of substances, called reactants, is converted to a new set of substances, called products
What is the literal meaning of stoichiometry?
“The measurement of elements”
Theoretical yield
The expected amounts of products (can be calculated)
Actual yield
The amount of product collected
Percent yield
The ratio of the actual yield to the theoretical yield
True or False:
Actual and theoretical yields can be expressed in different units when calculating percent yield
False, they must both be expressed in the same units (moles or masses)
Limiting reagant
The reagent whose amount (number of moles) is insufficient to react completely with all the other reagents, as determined by the stoichiometry of the reaction
