module 2: moles and calculations Flashcards
why is the theoretical yield of an experiment not achieved
- incomplete reaction
- side reactions may have taken place
- purifying the product could lead to some of the product being lost
- reversible reactions as the products can react with each other and form the reactants
why may percentage yield be over 100
- some water is left unevaporated
- impurities were formed
what is atom economy
it’s a measure of how well atoms have been utilised
how do you get a 100% atom economy?
use a reaction that only forms one product
find uses for the ‘waste’ products
what are isotopes
atoms of the same element that have the same numbers of protons and electrons but different numbers of neutrons
what is the mass number
the sum of protons and neutrons in an atom
what is the atomic number
the number of protons in an atom
what is meant by relative isotopic mass
it’s the mass of an isotope compared with 1/12 mass of a carbon-12 atom
what is meant by relative atomic mass
it’s the weighted mean mass of an atom compared with 1/12th mass of a carbon-12 atom
what equation links molecules, moles and Avagadrogo’s number
molecule = moles x Avagadro
what equation is used to calculate atomic mass based on isotopes
atomic mass based on isotopes = (isotope 1 x abundance 1) + (isotope 2 x abundance 2) / 100
what equation links the no. of moles and volume
(dm³)
no. of moles = volume (dm³) / 24
what equation links the no. of moles and volume
(cm³)
no. of moles = volume (cm³) / 24000
what is the conversion from cm³ to dm³ and vice versa
cm³ to dm³ = divide by 1000
dm³ to cm³ = multiply by 1000
what equation links concentration and volume and moles
moles = concentration (moldm-³) x volume (dm³)
what equation links volume, mass and concentration
mass = concentration (gdm-³) x volume (dm³)
how do you convert from gdm-³ to molsdm-³ and vice versa
gdm-³ to molsdm-³ = divide by Mr
molsdm-³ to gdm-³ = multiply by Mr
how do you calculate percentage yield
percentage yield = actual yield / theoretical yield x 100
how do you calculate atom economy
atom economy = Mr of desired product / Mr of all products x 100
what is an advantage of a high atom economy
less natural resources are used, meaning less waste
what is the ideal gas equation (with units)
pV=nRT
p = pressure, Pa
V = volume, m³
n = number of moles
R = the gas constant (8.31Jk^-1mol^-1)
T = temperature (K)
when is the ideal gas equation used
under conditions than 298K/25˚C and 1 atm pressure (10^5Pa) where volume of 1 mol of gas is 24dm³, the ideal gas equation must be used
define empirical formula
The simplest whole number ratio of atoms (of each element) present in a compound
what is the Celsius to kelvin conversion
celsius + 273
what are standard conditions
25˚C
1atm
1moldm^-3
order
dm³, cm³ and m³
smallest to largest
cm³
dm³
m³
how many grams are in a tonne
1,000,000
what is a salt
when the H+ of an acid is replaced with a metal/positive/ammonium ion
why is it important to develop sustainable reactions
low atom economies mean lots of waste is produced and it’s expensive to separate and dispose of the waste products safely
reactant chemicals are usually expensive and money is wasted if there are lots of waste products produced
low atom economies are less sustainable because they use up raw materials that are already in limited supply
reactions that can run at lower temperatures and pressure are cheaper and better to run for the environment
how would rinsing the burette with deionised water affect the titre
it wouldn’t, because the deionised water doesn’t react with the acid or change the number of moles of it
what even is Mr
the mass of 1 mol of a thing
molar mass!!!! durrrr
examples of weak acids
any carboxylic acids
examples of strong acids
not carboxylic acids
eg. hydrochloric, sulfuric, nitric
examples of strong bases
have OH in them
examples of weak bases
don’t have OH in them
outline the mechanism of hydroxynitrile formation
why is ice larger and less dense than water
Hydrogen bonds hold the water molecules further apart when frozen vs liquid and the bonds become rigid when frozen vs being constantly broken and reformed in water
