Topic 1.2 - Amount Of Substance Flashcards
(31 cards)
How many particles are there in one mole?
6.022x 10^23
How to calculate the number of particles?
Number of particles = moles x avogadro’s constant
How to calculate moles (with mass and Mr)
Mass (g) = moles (mol) x Mr
Define theoretical yield
The mass of a product that should be formed in a chemical reaction
What is the formula for percentage yield?
( Actual yield / theoretical yield ) x100
Why is actual yield always smaller than theoretical yield?
(3 reasons)
- Reaction may be reversible
- Product may be lost when it is separated from the mixture
- Reactants may react in other reactions
Define atom economy
A measure of the proportion of reactant atoms that become part of the desired on the balanced chemical equation
What does a high atom economy mean?
- Less money used in separating waste products from desired products
- Less waste products produced
- Less raw materials used
What is the formula for atom economy (%)
Atom economy (%) = Mr of desired product / Mr of total reactants
- When calculating Mr, include big numbers
Define a limiting reagent
The reactant that is not in excess
What is the formula to calculate moles (using concentration and volume) ?
Moles (mol) = concentration (moldm-3) x volume (dm3)
What are titrations used to find?
Fund an unknown concentration of an acid/alkali
Define a standard solution
- Any solution that you know the exact concentration of
- Dissolving a known amount of solid (e.g. sodium carbonate in a known amount of water to create a known concentration
What volume / concentration is found in the burette during titrations?
- Known volume
- Known concentration
What volume / concentration is found in the pipette/flask during titrations?
- Known volume
- Known concentration
What are two indicators used in titrations?
- Methyl orange
- Phenolphthalein
Define empirical formula
The simplest while number ratio of atoms of each element in a substance
Define molecular formula
A way of representing molecules that shows the number of atoms of each element in a molecule
Define an ionic equation
An equation which only shows the reacting particles of a reaction involving ions in solution
Define spectator ions
Ions that may not be involved in reactions involving ionic compounds dissolved in water
Why are precipitated formed in some reactions?
Some salts are insoluble in water
If solutions containing these ions are mixed, the insoluble salts form as a solid form as a solid precipitate
What is the ideal gas equation?
P (Pa) V (m3) = n (mol) R (8.31 J mol-1 K-1) T (K)
