Amount of substance Flashcards
What is the water of crystallisation?
- Water molecules existing within the crystal structures
What is Avogadro’s constant ?
- number of particles per moles
6.02 x 10^23
n = particles / AG
How to calculate water of crystallisation?
- calculate the mass of water + anhydrous salt
- work out the moles of both
- find the smallest whole number ratio
- n(salt) : n(H2O)
- value of n(H20) is the value in the formula.
How to calculate moles from mass?
n = mass (g) / Mr
How to calculate moles from conc?
n = C (moldm) x V (dm3)
or
n = C x V(cm3)x10-3
What is the ideal gas equation?
pV = nRT
p = Pa V = m3 n = mol R = 8.31 T = K
Ideal gas equation conversion units?
cm3
dm3
C
kPa
cm3 to m3 = x10^-6
dm3 to m3 = x10^-3
C to K = +273
kPa to Pa = x10^3
what are standard conditions?
298K
100kPa
How to calculate percentage yield?
Actual yield / theoretical yield X 100
why is yield never 100%
- reaction wasn’t completed
- side reactions
- loss of product during purification
What is atom economy and how to calculate it?
Mr of desired product / Mr of all products X 100
- how efficient a reaction is.
What is the importance of atom economy
- HAE means raw materials are used more efficiently ; more sustainable
- HAE means less by-products so less time + money spent separating these from desired product
- HAE produce less waste ; benefits environment.
Assumptions in the experimental formula of a hydrated salt?
- all water has been lost : heat to constant mass
- no further decomposition ; salts decompose further when heated (difficult to tell bc no colour change)
cm3 to ml
1cm3 = 1ml
dm3 to cm3 to ml to L
1dm3 = 1000cm3 = 1000ml = 1L
