Non-Wolsey Study Flashcards
Atomic mass is the
weighted average mass of an atom compared to C-12 (having 12 units)
Molecular mass is
the mass of a molecule compared to C-12 which has 12 units on the scale
Formula mass is
the mass of one formula unit of a compound compared to C-12 having 12 units on the scale
Isotopic mass
Mass of a particular isotope of an element compared to C-12 having 12 units on the scale
Define the term “Mole”
The amount of substance that has the same number of particles as there are atoms in exactly 12g of carbon-12 isotope.
1 Mole (mol) has exactly 6.02x10/\23 particles.
What is Avogadro’s constant
The number of atoms, ions, molecules or electrons in a Mole = 6.02x10/\23
Define “Empirical Formula”
gives the simplest ratio of different atoms present in a molecule
Define “Molecular Formula”
gives actual numbers of each type of atoms in a molecule
What is the triangle formula involving Mass, Molar Mass and Moles
M=m/n
Molar mass = Mass/Number of Moles
How do you calculate the volume of a gas at room temp.?
Moles x 24
At room temperature
What is the unit of volume of gas
dm/\3
1000cm/\3 = 1dm/\3
Triangle formula for concentration
C=n/V
Concentration = Number of Moles/Volume
Unit of concentration
mol dm/-3
What is this unit for: mol dm/-3
Concentration
Steps to calculate relative atomic mass from isotpoic mass and abundance
- Multiply each isotopic mass with its abundance %
- Add all the figures together
- Divide by 100
The formula for __ ______ compound is always its empirical formula
an ionic
The molecular formula for simple inorganic compounds are often…
the same
Organic molecules often have ________ empirical and molecular formulae
different
Organic compounds must be very ____ for combustion to calculate _______ ________
very pure, to calculate empirical formula
Steps for Empirical formula of magnesium oxide- compositional mass (0.486g)
- Burn known mass of Mg in excess oxygen (0.486g)
- Record the mass of Mg oxide formed (0.806g)
- Calculate the mass of the oxygen (0.806g - 0.486g) = 0.320g
- Calculate the mole ratio of Mg to O
Moles of Mg = 0.486/24.3 mol/-1 = 0.0200
Moles of O = 0.320/16.0 mol/-1 = 0.0200
Simplest ratio is 1:1 - Therefore empirical formula is MgO
Steps for empirical formula - combustion
- Note the mass of each element.
- Divide by atomic masses.
- Divide both by lowest figure.
- Empirical formula is the lowest whole number ratio.
What are spectator ions
Ions in an ionic reaction that do not interact - they are not included in ionic equations.
Balancing/writing ionic equations - Steps
- Write the full balanced equation
- Write down the ions present. (Any compounds are broken down into each element, and their charges are found by looking at the periodic table. Grp 1 = +, Grp 2 = 2+, Grp 6 = 2-, Grp 7 = -.
- Cancel out ions that appear the same on each side of equation (spectator ions)
- Re-write equation without the spectator ions
Steps for calculating concentration when given mass in g and volume in cm/\3.
- Change g to mol (g/Mr)
- Change cm3 to dm3 (cm/1000)
- Calculate concentration:
Number of moles in solute (mol)
——————————————- = concentration (mol dm3)
Volume of solution (dm-3)
Steps for calculating mass from concentration
- Re-arrange concentration equation to find number of moles (mol)
n (mol) = concentration (mol dm-3) x volume (dm3) - Multiply moles of solute by its molar mass
m of solute (g) = n (mol) x M (g mol-1)
Calculate mole ratio
mass/atomic mass
Divide both answers by the smallest answer and that is the mole ration.
Usually like them both to be whole numbers
