Moles Flashcards
The Mole
A group of entities (molecules, atoms, ions, electrons).
- It’s a really big number to represent a group of things.
- It’s viewed in scientific notation = 6.022x10^23
Avogadro’s Constant (Na)
- 6.022x10^23
- The value is chosen to define the number of atoms in exactly 12g of Carbon-12.
- Chemists count atoms by the mole instead of by the dozen.
Amount (n)
The quantity of a substance measured in moles.
Qualitative Analysis
The process of identifying substances present in a sample without the use of measurements.
Ex. Acid-base indicators, such as phenolphthalein, that turns colours at a given pH.
Quantitative Analysis
The process of measuring the quantity of a substance in a sample, providing numerical data (numbers).
Ex. The use of a digital pH meter.
Molar Mass (M)
- The mass of 1 or 6.022x10^23 particles of a substance.
- Measured in grams/mol (g/mol)
- The molar mass of a monatomic element (g/mol) is the SAME as the numerical value of the average ATOMIC MASS on the P.T. (Shown in amu).
- The molar mass of a monatomic element is EQUAL to the average atomic mass of that element; we just CHANGE the UNITS.
Ex.
Molar Mass of C = 12.01 g/mol
Atomic mass of C = 12.01 u
Molar Masses of Compounds
The SUM of the molar mass of each entity in the compound.
Ex. Calculate the Molar Mass of Water:
H2O
H - 2 (1.01 g/mol) = 2.02
O - 1 (16 g/mol) = 16
= 18.02 g/mol
Calculations Involving Molar Mass
- n = Represents amount of entities (# of moles)
- m = Represents a given mass in grams.
- M = Represents the molar mass of a substances in g/mol -> always look up in P.T.
Determining The Number of Entities (N)
• Use Avogadro’s Constant (6.02x10^23)!!
Ex. Determine the number of water molecules in a 1120 mg drop of water:
G • m = 1120 mg / 1000 = 1.12g
M = H2O = 18.02 g/mol
R • N = ? , n = ?
A • n = m/M
S • n = 1.12g / 18.02 g/mol = 0.0621531 mol
N = (0.0621531) (6.022x10^23)
= 3.74x10^22 molecules
