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Topic 1. Stoichiometric relationships

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Element V.S. Atom V.S. Compound V.S. Mixture

Element: composed of atoms that all have the same atomic number

  • ex. carbon

Atom: the smallest unit of matter​

Compound: 2+ elements that are chemically bonded

  • ex. H2O, CO2

Mixture: 2+ elements/compounds that are not chemically bonded

  • homogeneous mixtures have uniform properties

  • heterogeneous mixtures have non-uniform properties


From Ms. Fu's powerpoint

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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.

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Example question:

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.

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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.

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Stoichiometric relationships (very important)

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When solving problems about complete combustion, knowing this equation comes in handy.

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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)

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Solving parts per million problems

Parts per million (ppm) is a unit of concentration (mass to mass) → represented as 1g / 10 g

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Other important calculations:

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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.

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