Chapter 3 - Amount of a substance Flashcards
What is ‘molar mass’ and what are it’s units?
Gives the mass in grams in each mole of the substance. Units are gmol^-1
What is the formula for amount of a substance (n)?
mass (m) / molar mass (M)
What is the definition of ‘molecular formulae’?
The number of atoms of each element in a molecule.
What is the definition of ‘empirical formulae’?
The simplest whole number ratio of atoms of each element in a compound.
What five rows are needed when calculating empirical formula in a table?
• Elements
• Mass or %
• Mass number
• Moles
• Ratio
What additional three rows are needed when calculating the molecular formula?
• Mass of the empirical formula
• Mr / mass of empirical formula
• Times answer with numbers in empirical formula
What is the definition of ‘water of crystallisation’?
Water molecules that form an essential part of the crystalline structure of the compound.
What are two assumptions made from experimental formulae?
All the water has been lost and there is no further decomposition.
What is the definition and units of concentration?
The amount of solute, in moles, dissolved in each 1dm^3 of solution.
Units = moldm^-3
What is equation with concentration, number of moles and volume?
number of moles= concentration x volume
How do you get from a concentration in moldm to mass concentration?
Times it by the Mr.
What are the four assumptions for the molecules making up an ideal gas?
Random motion, elastic collisions, negligible size and no intermolecular forces.
What is the ideal gas equation?
pV=nRT
What is the conversion to cm^3 to m^3?
x10^-6
What is conversion from dm^3 to m^3?
x10^-3
