Module 2: Amount Of Substance Atoms Ions And Compounds Flashcards
What is the structure of an atom
Protons and neutrons in nucleus and electrons in shells
What is the charge of a proton
+1
What is the charge of an neutron
0
What the charge of an electron
-1
What is the mass of a proton
1
What is the mass of a neutron
1
What is the mass of an electron
1/1836
What is the overall charge of an atom and why
Neutral because the total positive charge from protons is equal to the negative charge from electrons
Definition for a mole
Amount of substance containing as many particles as there are carbon atoms in exactly 12g of the C-12 isotope
definition for relative atomic mass
Weighted mean mass of an atom of an element compared to 1/12th of the mass of an atom if C-12
Definition for relative isotopic mass
Weighted mean mass of an atom of an isotope when compare to 1/12th mass of an atom of C-12
What molar mass
Mass mole of a substance (g mol-1)
Definition for relative molecular mass
Weighted mean mass of a molecule compared to 1/12 of the mass of an atom of C-12
What’s avogadros constant
Number of atom per mole of the C-12 isotope (6.02 x 10^23 )
How do you do a reacting mass calculation when given 1 mass
Whilst using balanced equation and correct units
1. Mole of known (mol = mass/mr)
2. Mole of unknown (mole ratio)
3. Mass of unknown (mass = mol x mr
What is the solid equation for moles
Mole= mass (g) / Mr
What is a limiting reagent
Substance in reaction which runs out first
How do you do a limiting reagent mass calculation when given 2 masses
Using balanced equation and correct units
1. Mol of both reagents (mol = mass/mr)
2. Find limiting reagent
3. Mol of unknown (mol ratio)
4. Mass of unknown (mass =mol x mr )
What’s an empirical formula
Simplest whole number ratio of atoms present in a compound
What molecular formula
Number of atoms of each element in a molecule
How to calculate empirical formula
- Table with each element
- Write % or mass (g)
- Find moles of each elements (mol=mass/mr)
- Find whole number ratio (divide by smallest)
- Formula
What does anhydrous mean
Substance that contains no water molecules
What dies hydrated mean
Crystalline and containing water molecules
What is water of crystallisation
Water molecules that form essential part of the crystalline structure of a compound
How do you calculate formula for a hydrated salt
- Moles of anhydrous (mol=mass/mr)
2 moles of water (mol=mass/mr) - Ratio to find formula (empirical method)
What is the practical for water of crystallisation
-mass of crucible
-mass of crucible and hydrated salt
-heat until constant mass (reweigh x2)
-record mass
-mass of anhydrous
-find formula
Equation for moles in solution
Moles=conc (mol dm-3) x vol (dm^3)
Equation for moles in gas
Moles = vol(dm^3) / 24
What has to be for mol = vol/24 to be true
Room temp of 298K and room pressure (101kPa)
What’s the ideal gas equation
pV = nRT
What’s p in pV = nRT
Pressure in Pa
What’s V in pV = nRT
Volume in m^3
What’s n in pV = nRT
Number of moles
What’s R in pV = nRT
Ideal gas constant of 8.314 J mol-1 K-1
What’s T in pV=nRT
Temperature in K
How do you convert °C to K
+ 273
Percentage yield equation
% yield = actual yield (mol of product)
—————————————- ——-x 100
Theoretical yield (mol of products
What can result in lowered percentage yield
-incomplete reaction
-side reaction
-impure substance
-loss through transference
What is atom economy
Measure of what proportion of a reaction are the desired product and how much is waster
Atom economy equation
Mass of desired product
—————————————x 100
Total mass of product
What is true for atom economy if only 1 product
100% atom economy and is ideal
What can be used to analyse different elements
Mass spectrometry
What can mass spectra show
Relative isotopic masses and abundances
What is on the axis for mass spectrum
X axis- mass/charge
Y axis -%isotope abundance
What is the equation for relative atomic mass
(% x isotopic mass) + ( % x isotopic mass)
———————————————————
100
