2.2 - Amount of substance Flashcards
Define the term ‘Avagadro’s constant’ ?
Avagadro’s constant - The number of atoms per mole of the carbon-12 isotope ( 6.022 x 10^23 mol-1 )
Define the term ‘amount of substance’ ?
Amount of substance - The quantity whose unit of the mole, used as a means of counting any species such as atoms, ions and molecules
Define the term ‘mole’ ?
Mole - The amount of any substance contain gin as many elementary particles as there are carbon atoms in exactly 12g of carbon-12 isotope ( 6.022 x 10^23 )
Define the term ‘Molar mass’ ?
Molar mass - The mass per mole of a substance, in units of gmol-1
Define the term ‘Molar gas volume’ ?
Molar gas volume - The volume per mole of gas molecules at a stated temperature and pressure
Define the term ‘anhydrous’ ?
Anhydrous - Containing no water molecules
Define the term ‘hydrated’ ?
Hydrated - A crystalline compound containing water
Define the term ‘water of crystallisation’ ?
Water of crystallisation - Water molecules that are bonded into a crystalline structure of a compound
What is the units for molar mass ?
g mol^–1
What is molar gas volume ?
Gas volume per mole
What are the units for molar gas volume ?
dm^3 mol^-1
Define the term ‘Empirical formula’ ?
Empirical formula - The formula that shows the simplest whole number ratio of atoms of each element present in a compound
Define the term ‘molecular formula’ ?
Molecular formula - A formula that shows the number and type of atoms of each element present in a molecule
Do you know how to calculate the empirical formula and molecular formula ?
Yes
Do you know how to do calculations using mass or gas volume or solution volume and concentration ?
Yes
What is the ideal gas equation ?
pV = nRT
What is a percentage error ?
Percentage error is the error of the actual data recorded
What is the equation to calculate percentage error ?
Percentage error = ( uncertainty/ value measured ) x 100
What do you times by two when calculating the percentage error of titre from a burette ?
- To achieve a titre from a burette you need to take away the initial reading from the final reading
- Therefore, this involves two values which means there are two uncertainties
- Therefore, you times by two when calculating percentage error
How do you find the uncertainty for a particular piece of equipment ?
- Find the lower and upper bound of the data recorded
- Find the difference between actual data and the lower/ upper bound
What needs to be considered when designing an experiment ?
- Atom economy ( Ideally one product or market found for by-product so 100% )
- Percentage yield ( Very difficult to have high yield of reaction is reversible )
- Sustainability
Define the term ‘percentage yield’ ?
Percentage yield - The ratio of mass of actual product made to the maximum theoretical mass of product
Do you know how to calculate the atom economy or percentage yield ?
Yes
Define the term ‘atom economy’ ?
Atom economy - The ratio of reactants used to make the desired product. The higher the atom economy, the less waste/ by-product.
When is a reaction ‘sustainable’ ?
- When the raw materials are renewable ( eg. Sugarcane, solar panels, water … )
- When the products don’t damage the environment
Describe how to produce a standard solution ( 100cm^3, 0.20 mol/dm^-3 of NAv2COv3 )
1 ) Work out the mass of Nav2COv3 required
2 ) Transfer the solid into a small beaker and dissolve in a minimum volume of distilled water, stir with a glass rod
3 ) Transfer via funnel ( to prvenet loss/escape ) into a 100cm^3 volume metric flask
4 ) Rinse stirring rod and beaker three times with distilled water and rinse funnel
5 ) Add distilled water just below the line, then use a dropping pipette to add water until the bottom of the meniscus
6 ) Put a stopper and shake to mix the solution
