Topic 1. Stoichiometric relationships
Element V.S. Atom V.S. Compound V.S. Mixture
Element: composed of atoms that all have the same atomic number
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ex. carbon
Atom: the smallest unit of matter
Compound: 2+ elements that are chemically bonded
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ex. H2O, CO2
Mixture: 2+ elements/compounds that are not chemically bonded
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homogeneous mixtures have uniform properties
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heterogeneous mixtures have non-uniform properties
From Ms. Fu's powerpoint
Compounds
Molar mass
Molar mass can be defined as the mass in 1 mol → unit is g/mol
Calculating relative atomic mass
Relative atomic mass (Ar) is the sum of the weighted average of the atomic mass of the known isotopes of an element.
Example question:
From smashingscience.org
0.7860*24 + 0.1011*25 + 0.1129*26 = 24.33
Ideal Gas Law
The units kPa and dm³ go together
The units Pa and m³ go together.
Avogadro's Law states that the number of gaseous moles is proportional to the volume of the gas.
Gases behave more like ideal gases in low pressures (no attraction) and high temperatures.
Stoichiometric relationships (very important)
When solving problems about complete combustion, knowing this equation comes in handy.
Deriving density from PV=nRT
Solving concentration problems
The unit for concentration is mol/dm³ and can be calculated with this equation:
Method 1) use the equations n = m/M and c = n/V
Method 2) C₁V₁ = k C₂V₂ (where k is the mole ratio)
Solving parts per million problems
Parts per million (ppm) is a unit of concentration (mass to mass) → represented as 1g / 10⁶ g
Other important calculations:
In titration, there are two solutions: one solution with a known concentration and volume & one solution with an unknown concentration and volume.
Through titration, we can determine the volume of the unknown solution, and thus calculate its concentration.
Use the C₁V₁ = k C₂V₂ equation.
