✨Module 2: Amount of substance Flashcards
Define mole.
Amount of any substance containing 6.02 x 10^23 particles.
One mole of carbon is …
Mass 12g.
Define Avogadro’s constant.
No. atoms per mole in 12g of carbon-12.
Particles =
Moles x 6.02x10^23
Define molar mass.
Mass per mole of substance. gmol-1
Moles =
Mass in g/molar mass
Define molar gas volume.
Gas volume per mole at a stated temp and pressure. At RTP, it is 24dm3mol-1.
RTP is …
20 degrees C and 101kPa.
Volume in dm3 =
Moles x 24dm3/24000cm3
Moles =
Conc (moldm-3) x volume in solution (dm3)
Temp in Kelvin?
Degrees in C + 273
Each 1K rise in temp is the same as …
1 degrees C rise in temp.
Binary compound contains …
2 elements - use the name of the 1st element and change the name of the 2nd element to -ide.
Polyatomic ions contain …
Atoms of more than 1 element.
Nitrate/nitrite -
Manganate -
Phosphate -
Hydrogen carbonate -
NO3-/NO2-
MnO4-
PO43-
HCO3-
What does (aq) state symbol mean?
Dissolved in water.
Rules for balancing equations?
Can use decimals, always use state symbols.
Nitrogen/phosphorus/sulfur.
N2, P4, S8.
Ammonia + acid =
Ammonium salt.
NH3 + HCl = NH4Cl
Metal carbonate decomposes (with heat) to
Metal oxide and carbon dioxide.
CaCO3 = CaO + CO2
Define water of crystallisation.
Water molecules that are bonded to a crystal lattice e.g. NaCl.
The solid salt containing WOC is …
Anhydrous substance has …
Hydrated.
No WOC.
When blue crystals of hydrated copper sulphate are heated …
Bonds holding water together break and leaves anhydrous copper sulphate.
Anhydrous copper sulphate may be pale blue because …
It’s hard to get rid of last traces of water.
Experiment for water of crystallisation?
- Weigh empty crucible, then reweigh with hydrated salt.
- Use pipe clay triangle to support crucible on tripod. Heat contents.
- Leave to cool then reweigh crucible and anhydrous salt.
How long do you heat the contents for?
Crystals are heated repeatedly until mass of residue no longer changes, suggesting all water has been removed.
Define empirical formula.
Simplest whole number ratio of atoms in a compound. Useful for giant structures.
When finding empirical formula …
Find the ratio of moles.
Define theoretical yield.
Maximum amount of product formed.
Actual yield is always …
Less than theoretical/% yield never 100%.
Why is this?
- Loss of products on equipment e.g. filter paper.
- Reaction is incomplete.
- Unwanted side reactions.
Percentage yield =
Actual/Theoretical x 100
Atom economy measures …
How much reactant atoms become desired product.
% atom economy =
RFM of desired product/RFM of all products all x100
Atom economy if there’s only 1 product?
100% as all atoms are used up.
Why is a higher atom economy better?
Reduces waste, preserves raw materials.
What about lower atom economy?
More expensive as it costs more to dispose waste products safely.
