Chapter 3 - keywords

Amount of substance

The quantity whose unit of the mole, used as means of counting any species such as atoms, ions and molecules.

Mole

The amount of any substance containing as many elementary particles as there are carbon atoms in exactly 12g of the carbon-12 isotope (that’s 6.02 × 10²³)

Avogadro’s constant

The no. of atoms per mole of the carbon-12 isotope (6.02 × 10²³ mol ^-1)

Molar mass

The mass per mole of a substance, in units of g mol^-1

Molecular formula

Formula that shows the no. and type of atoms of each element present in a molecule.

Empirical formula

Formula that shows the simplest whole-number ration of atoms of each element present in a compound.

Relative molecular mass

The weighted mean mass of a molecule of a compound compared with 1/12th of the mass of an atom of carbon-12.

Relative formula mass

The weighted mean mass of a formula unit of a impound compared with 1/12th of the mass of an atom of carbon-12.

Hydrated

A crystalline compound containing water molecules.

Anhydrous

Containing no water molecules.

Molecular gas Volume

The volume per mole of gas molecules at a stated temp + press.

Ideal gas equation

PV = nRT

P = Pressure = Pascals = 101325Pa

V = Volume = m³

n = no. of moles

R = Ideal gas constant = 8.31 J mol^-1 K^-1

T = Temp = Kelvins = degrees c to K +273

Stoichiometry

The ration of the amount (moles) of each substance in a chemical equation (essentially the ration of balancing numbers).

Percentage Yield formula

Percentage yield = actual yield/theoretical yield x 100%

Why is it difficult to achieve a full yield?

• reaction may not have gone to completion

• Other reactions (side reactions) may have taken place alongside the main reaction

• Purification of the product may result in loss of some product

Limiting reagent

The reactant that is not in excess, which will be used up first and stop the reaction.

Atom economy + formula

Atom economy = sum of molar masses of desired products/ sum of molar masses of all products x 100%

What does reactions w/ high atom economy mean?

• produce a large proportion of desired products and few unwanted waste products

• Are important for sustainability as they make the best use of natural resources

What does efficiency depend on?

Atom economy and percentage yield

Molecular ions

Hydroxide (OH-)

Nitrate (NO3 -)

Ammonium (NH4 +)

Sulfate (SO4 2-)

Carbonate (CO3 2-)