(PMT) Amount of substance Flashcards
What is the symbol for amount
of substance?
n
What is the unit used to
measure amount of
substance?
Mole
What does the Avogadro
constant represent?
The number of atoms per mole of the
carbon-12 isotope
How to calculate the mass of 1
mole of the element?
Mass of 1 mole = relative atomic mass in
grams
How to calculate moles when
mass and molar mass are
given?
Moles (mol) = mass (g) / molar mass or Mr (g mol -1)
State Avogadro’s law
Under the same temperature and
pressure, one mole of any gas would
occupy the same volume.
How much volume does a gas
occupy, at room temperature
and pressure?
24 dm3
or 24000 cm3
Define molar gas volume
The volume per mole of gas molecules
Why do different gas particles
occupy the same volume?
The gas particles are very spread out,
hence individual differences has no
effect.
How to calculate moles when
gas volume is given?
Moles (mol) = volume (dm3 ) / 24 Or Moles (mol) = volume (cm3 ) / 24000
What are the ideal ways in
which gases behave? (5)
● They are in continuous motion
● No intermolecular forces experienced
● Exert pressure when they collide with each other or
container
● No kinetic energy is lost in the collisions
● When temperature increases, kinetic energy of gases also
increase
Write down the ideal gas
equation (in words and
symbols, including the units)
pV = nRT Pressure (Pa) x volume (m3 ) = number of moles (mol) x gas constant (8.314 J mol-1)x temperature (K)
1 atmospheric pressure is
equal to how many pascal?
1 atm = 101325 Pa
0℃ is equal to how many
kelvin?
273 K
What does concentration of a
solution mean?
It is the amount of solute dissolved in 1
dm3
of solvent
How do you calculate moles
when concentration and
volume are given?
Moles (mol) = concentration (mol dm-3) x
volume (dm3
)
What is a standard solution?
A solution of known concentration
Write down the steps to
prepare a standard solution
- Weigh the solute using the weigh by difference method in a weighing boat
- In a beaker dissolve the solute using the solvent
- Pour the solution into a 250cm3 volumetric flask
- Rinse the beaker using the solution and add it to the flask (repeat 10x adding in all the washings)
- Add solvent to the flask carefully until bottom of the meniscus is on the calibration mark
- Mix the solution thoroughly to ensure complete mixing (invert 10x with a lid on)
What do the terms
concentrated and dilute
mean?
Concentrated - large amount of solute per dm3 of solvent Dilute - small amount of solute per dm3 of solvent
What is a species in a
chemical reaction?
Any particle that takes part in a reaction
What are the four common
state symbols?
- Solid (s)
- Liquid (l)
- Gaseous (g)
- Aqueous (aq)
What does the percentage
yield mean?
The efficiency of which reactants are
converted into products.
What are the reasons for not
obtaining 100% yield? (5)
● Reaction may be at equilibrium (reversible)
● The reactants may be impure
● Side reactions could happen
● Reactants or products may be left behind while
transferring
● Loss of products during separation and purification
How is percentage yield
calculated?
Percentage yield = (actual amount of
product (mol or g) / theoretical amount of
product (mol or g)) x 100
