- Created by: Priscilla
- Created on: 23-04-11 11:02
The Mole concept and Avogadro's constant
The mole concept applies to all kinds of particles: atoms, molecules, ions, electrons, formula units, and so on. The amount of substance is measured in moles (mol). The approximate value of Avogadro’s constant (L), 6.02 × 10^23mol^–1, should be known.
n = m / Mr
n = N (number of particles) / 6.02 X 10^23
CHEMICAL FORMULA is the number of each type of atom in the smallest viable unit of the substance.
EMPIRICAL FORMULA is the simplest possible ratio of elements in a substance.
Example - 2.476g of an oxide of copper is found to contain 2.199g of copper. What is its empirical formula?
1. Divide each mass by its Mr to find the moles
Oxygen - 0.277 / 16.00 = 0.01731mol
Copper - 2.199 / 63.55 = 0.03460mol
2. Divide by the smallest number to find the ratio
1:1.999 therefore, 1:2
Example 2 - Find the molecular formula of CH^2O which has the molecular mas of 60.
Divide the molecular mass with the relative molecular mass:
60/2 = 30.0
Therefore, the molecular mass is twice the empirical formula.
CH^2O -> C^2 H^4 O^2
The balancing numbers are known as the coefficients of the reaction.
Use of the balancing number is essential to fulfill the law of conservation of matter.
The stoichiometry is the overall set of balancing coefficients of a chemical reaction.
Mass and gaseous volume relationships in chemical
THEORETICAL YIELD = n x M
Experimental Yield = m / Theoretical yield x 100
For RTP - n = v / 24,000 cm^3
For STP - n = v / 22,400 cm^3
c = n/v