2.1.3 Amount of Substance Flashcards
What is the symbol for the amount of substance?
n
What is the unit used to measure the 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 an 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 occupies 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?
Gas particles are very spread out, so individual differences have no effect
How to calculate moles when gas volume is given?
Moles (mol) = volume (dm³) / 24
Moles (mol) = volume (cm³) / 24000
What are the ideal ways in which gases behave?
- They are in continuous motion
- No intermolecular forces experienced
- Exert pressure when colliding with each other or the container
- No kinetic energy is lost in collisions
- Kinetic energy increases with temperature
Write down the ideal gas equation (in words and symbols, including units).
pV = nRT Pressure (Pa) × volume (m³) = number of moles (mol) × gas constant (8.314 J mol⁻¹ K⁻¹) × temperature (K)
1 atmospheric pressure equals how many pascals?
1 atm = 101325 Pa
0°C is equal to how many kelvin?
273 K
What does the concentration of a solution mean?
The amount of solute dissolved in 1 dm³ of solvent
How to calculate moles when concentration and volume are given?
Moles (mol) = concentration (mol dm⁻³) × volume (dm³)
What is a standard solution?
A solution of known concentration
Write the steps to prepare a standard solution.
- Weigh the solute using the weigh-by-difference method
- Dissolve the solute in a beaker with the solvent
- Transfer the solution into a volumetric flask
- Rinse the beaker and add the rinsings to the flask
- Add solvent until the flask reaches the graduation line
- Mix thoroughly to ensure complete mixing
Define the terms ‘concentrated’ and ‘dilute.’
- 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)
- Gas (g)
- Aqueous (aq)
What does percentage yield mean?
The efficiency with which reactants are converted into products
What are the reasons for not obtaining 100% yield?
- Reaction may be at equilibrium
- Reactants may be impure
- Side reactions could occur
- Reactants or products may be lost during transfer
- Loss of products during separation and purification
How is percentage yield calculated?
Percentage yield = (actual amount of product (mol) / theoretical amount of product (mol)) × 100
What does atom economy tell us about?
The proportion of desired products compared with all the products formed in the reaction
How is atom economy calculated?
Atom economy = (molecular mass of desired product / sum of molecular masses of all products) × 100
Does 100% yield mean 100% atom economy?
No, because not all products formed in the reaction may be the desired products
Which type of reaction has 100% atom economy?
Addition reactions (two or more reactants combine to form a single product)
