2.0 Amount of substance Flashcards
(24 cards)
What is the relative atomic mass of an atom?
The average mass of an atom of an element (taking into account its naturally occurring isotopes) relative to 1/12th the relative atomic mass of an atom of carbon-12
What is the relative molecular mass of a molecule?
The average mass of a molecule compared to 1/12th the relative mass of an tom of carbon-12
What is the Avogadro constant and what is its numerical value?
The number of atoms in 12g of carbon 12
6.022 x 10^23
What is a mole?
The amount of substance that contains 6.022 x 10^23 particles
What is the equation used to calculate the number of particles in a substance from its number of moles?
P = nL
Particles = moles x Avogardo constant
What is the equation used to calculate the number of moles from its mass?
N = m/M
Moles = mass/Mr
What two units are used for concentration of a solution?
mol dm⁻³ and g dm⁻³
What is the equation used to calculate the concentration of a solution?
Concentration = n x 1000/ volume
State the ideal gas equation
PV = nRT
Give the units for P, V, and T
P = pascals
V = m^3
T = kelvin
What does R stand for in the ideal gas equation?
The gas constant
What is the molecular formula?
The actual number of atoms of each element in a compound
What is the empirical formula?
The simplest whole number ratio of atoms of each element in a compound
How do you calculate the empirical formula of a compound given the masses of each element?
- Work out the number of moles of each element
- Work out the ratios of each element by dividing the moles of each element by the smallest number of moles
- Simplify the ratios and write the empirical formula
How do you determine the formula of an ionic compound?
use the charges on the ions to work out how many of each ion are necessary to result in no net charge
What is an ionic equation?
A simplified equation showing the ions present in a reaction
What is a spectator ion?
An ion that does not take part in a reaction
Which substance produces ions in an ionic equation?
The aqueous solutions of ionic compounds
What are concordant titres?
Titres within 0.1cm^3 of each other
What colour is phenolphthalein in acid and alkali?
Colourless in acid
Purple in alkali
How do calculate the concentration of an unknown from titration of a known solution?
- Establish reaction ratio from the balanced equation
- Determine number of moles of known (standard) solution
- Determine moles of unknown solution needed using reaction ratio
- Calculate concentration from the volume of unknown solution
What is the percentage yield of a chemical reaction?
How much product is actually made compared with the amount of product that was expected, calculated using reacting masses
What equation is used to calculate the percentage yield of a reaction
Actual yield/Theoretical yield x 100
What equation is used to calculate the atom economy of a reaction?
mr of desired product/sum of reactants Mr x 100
