Topic 1: Stoichiometry Flashcards
What is a homogenous mixture
All substances in mixture in the same phase (NOT STATE) essentially everything is mixed so well you can’t see the difference between them - no visible boundary separating it into parts.
What is a heterogenous mixture
Substances all in different phases
Mixtures and their individual properties
They retain their individual properties/they are not chemically bonded
Describe a solid
Fixed shape
Can vibrate about a fixed point
Heat can cause enough vibration to overcome attractive forces –> melts
Describe a liquid
Takes shape of container, fixed volume
Has translational velocity (diffusion)
Heat and pressure of vapour can cause it to boil and evaporate
Describe a gas
Widely spaced particles, fill container
Pressure in a container is caused by collisions with the container
IMF is negligible
Solid to gas
Sublimation
Gas to solid
deposition
liquid to gas without boiling
vaporization
Liquid to solid
freezing
gas to liquid
condensation
is vaporization endo or exo
endothermic because it absorbs energy to increase kinetic energy to change to a vapour
What is avagadros constant
6.02 *10^23
What is an isotope
Same amount of protons and electrons but different mass –> different amount of neutrons
Symbol for relative mass
Mr
Mole to atoms
1 mole to 6.02*10^23 atoms
mole to mass to molar mass formula
n = mass(g) /molar mass (g/mol)
Empirical formula
The smallest whole number ratio of atoms in an element
How to calculate empirical formula given percentage mass
- assume 100 g total and change each percentage to grams
- convert to mols by dividing by molar mass
- find ratio between the grams and multiply accordingly
How to calculate molecular formula from empirical formula given its molar mass
- divide given molar mass by the mass of the empirical formula
- multiply subscripts by the number found in step 1
What is a precipitate
insoluble ionic solid
Density of liquid formula
Mass (g)/Volume (cm^3)
Ideal gas law and all of the units
PV = nRT
Pressure (1 atm - 1.013 * 10^5 Pa)
Volume (1 m^3 - 1000 litres)
Moles
R constant (8.314 J/K*mol)
Temperature (kelvin)
What are moles represented by in an equation
the coefficients in front of them
what does (aq) mean
in aqueous solution
Properties of chemical reactions
- new substances are formed
- Bonds in the reactants are broken and bonds int he products are formed resulting in an energy change between the reacting system and its surroundings
- There is a fixed relationships between the number of particles of reactants and products –> no overall change in mass
What are net ionic equations
Only show species between oxidized or reduced - elimination of spectator ions
- write molecule equation
- write complete ionic equation showing all aqueous species broken down into their ions
- cancel out spectator ions that appear on both sides.
When to use ionic equations and why
When dealing with ionic compounds because they completely dissociate in solution
units of concentration/formula
C=n/V (mols dm^-3)
[ ] meaning
concentration
At constant temperature what happens between volume and pressure
Volume decrease causes increase in gas concentration and pressure from collisions with container walls. Therefore greater pressure. Pressure increase is inversely proportional to decrease in volume
when does a gas behave most like an ideal gas?
At high temperatures and low pressures
At stp what volume does one mol of gas occupy
22.7 dm^3 or 22.7 * 10^-2 m^3
Atom economy formula
atom economy = mass of desired products/mass of all products * 100
Magnitude of atom economy meaning
high atom economy means that fewer natural resources are used and less waste is created
Percentage yield formula?
Actual yield/theoretical yield * 100
Percentage change formula
(Final - initial) / initial * 100
percentage error calculation
(actual value - expected value)/expected value * 100
