Chapter 3
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How are chemicals measured?
1) mass 2) volume
What is one mole?
The amount of a substance that contains 6.02x10^23 particles
What is the Avogadro constant?
6.01x10²³, the number of particles in each mole of carbon-12
What is the mass of one mole of carbon, C?
12.0g
What is the mass of one mole of hydrogen, H?
1.0g
What is molar mass, M?
The mass per mole of a substance
What are the units of molar mass?
g mol^-1
amount, n =
mass, m / molar mass, M
What is a molecule?
Two or more atoms held together by covalent bonds
What is molecular formula?
The number of atoms of each element in a molecule
What is empirical formula?
The simplest whole-number ratio of atoms of each element in a compound
What is relative molecular mass, Mr?
The comparison of the mass of a molecule with the mass of an atom of carbon-12
What is relative formula mass?
The comparison of the mass of a formula unit with the mass of an atom of carbon-12
How do you calculate relative formula mass?
By adding together the relative atomic masses of the elements in the empirical formula
How do you calculate relative molecular mass?
By adding together relative molecular masses of the elements making up a molecule
What does it mean when crystals are hydrated?
Water molecules are part of their crystalline structure
What is water of crystallisation?
Water molecules that are bonded into a crystalline structure of a compound
What is the formula of the reaction where hydrated copper(II) sulfate is heated?
CuSO₄•5H₂O(s) → CuSO₄(s) + 5H₂O(l)
What would happen if there was no water in copper(II) sulfate?
1) the crystalline structure would be lost 2) a white powder would remain
What are the 2 assumptions made when determining that an experimental formula is accurate?
1) all of the water has been lost 2) no further decomposition
What does it mean when the hydrated and anhydrous forms have different colours?
You can be fairly sure when all of the water has been removed
How can you check that all water has been removed?
Heat to constant mass - repeatedly reheat until the mass of the residue no longer changes
How are liquids and gases measured?
By volume
How do you measure the mass of a solution or a gas?
Convert the volume into amount of substance, in moles to be able to count the particles present