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 (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)
● 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
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 sample bottle containing solid
- Transfer sample into beaker and reweigh
- Record mass difference
- Add distilled water and stir it with a glass rod until all dissolved
- Transfer to volumetric flask with washings
- Make up to 250cm3 mark by adding distilled water
- Shake flask
What does the term
concentrated mean?
Large amount of solute per dm3 of solvent
What does the term
dilute mean?
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
● The reactants may be impure
● Side reactions could happen
● Reactants/products may be left behind while
transferring
● Loss of products during separation and purification
How is percentage yield calculated?
actual amount of
product (mol) / theoretical amount of
product (mol) x 100
What does atom economy tell us?
The proportion of desired products
compared with all the products formed in
the reaction
How is atom economy calculated?
Mr of desired product / sum of the Mr’s of all products x 100
Does 100% yield mean 100% atom economy?
No, even if all the reactants are
converted into products, not all products of the reaction will be the required products
Which type of reaction has 100% atom economy?
Addition reactions (two or more reactants are combined to form a product)
