Structure 1.4
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What is a mole?
The amount of a substance that contains as many specified particles as there are atoms in exactly 12g of carbon-12
How many particles in one mole of a substance?
Avogardo’s Constant / 6.02 x 10^23
What is the equation that converts number of particles to number of moles?
number of moles (n) = number of particles (N) / avogardo’s constant (NA)
What is the formula for mole ratio?
Number of a specific particle per a specific substance
What is the relative atomic mass of an element (Ar)?
The weighted average of its isotopic masses, according to their relative abundances, relative to 1/12 of the mass of a carbon-12 atom.
What is the relative formula mass (Mr)?
The sum of the relative atomic masses of the atoms as given in the chemical formula of a species
What is the relative molecular mass (Mr)?
the mass of a molecule relative to 1/12 the mass of a carbon-12 atom
What is molar mass?
The mass of one mole of a substance (M, g mol-1)
What is the formula for converting mass to number of moles?
number of moles (n) = mass (m) / molar mass (M)
What does the empirical formula of a compound give?
The simplest ratio of atoms of each element present in that compound
What does the molecular formula of a compound give?
The actual number of atoms of each element present in a molecule
How can the molecular formula be found from the empirical formula?
(Molecular formula mass / empirical formula mass ) x empirical formula
What is the percentage composition by mass of a compound?
The proportion of the total mass of the compound accounted for by the mass of each element
What is the formula for percentage composition by mass?
%Element = m(element)/m(compound) x 100%
What is the formula for percentager composition by mass, using the chemical formula?
%Element = M(element) / M(compound) x 100%
How can the molar mass of a compound be found?
Adding the relative atomic masses of the elemtns in the compound
What is the molecular formula reserved for?
Covalent molecular species
With ionic substances, what is the empirical formula the same as?
the ionic formula
How can masses be used to find the empirical formula?
Objective: find the simplest whole number ratio of the number of moles of each element in a substance steps - Identify the mass of each element - Calculate the moles of each element - Divide by the smallest number of moles - Find the simplest whole number ratio - Find the EF
How can the percentage composition by mass be used to find the EF?
Assume the mass is 100g, and follow the normal steps
How is relative empirical formula mass (EFr) calculated?
Adding the relative atomic masses of the atoms in the empirical formula together
What is the IB Chemistry unit for quantifies volumes?
cm3 / dm3 1000 cm3 = 1 dm3
What is the formula for concentration as mass per volume?
C = m (g) / V (dm3)
What is the formula for concentration as moles per volume?
C = n (mol) / V (dm3)