2.1.3 - Amount of Substance
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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 dm^3 24000 cm^3
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 (dm^3) / 24 or moles (mol) = volume (cm^3) / 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 (m^3) = number of moles (mol) x gas con stant (8.314 Jmol-1) x temperature (k)
1 atmospheric pressure is equal to how many pascals?
1 atm = 101325 Pa
0 degrees celcius is equal to how many kelvin?
273 k
What does concentration of a solution mean?
It is the amount of solute dissolved in 1 dm^3 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 beaker dissolve the solute using the solvent • Pour the solution into a volumetric flask • Rin se the beaker using the solution and ass it to the flask • Add solvent to the flask carefully until it reaches the graduation line • Mix the solution thoroughly to ensure complete mixing
What does the terms concentrated and dilute mean?
concentrated - large amount of solute per dm^3 of solvent dilute - small amount of solute per dm^3 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 ay be at equilibrium • 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) / theoretical amount of product (mol) ) x 100