Topic 1: Stoichiometric Relationships Flashcards
element
A sample substance composed of a single type of atom
isotope
Atoms of the same element, having the same no. of protons, but with differing no. of neutrons
compound
A mixture of elements in which atoms of various elements chemically combine together in a fixed ratio
vapor pressure
The pressure that a liquid’s gaseous form exerts in a closed environment
Outline the liquid-vapour equilibrium
A liquid in an enclosed chamber will form a dynamic equilibrium with its own vapor:
- fast-moving particles in the liquid escape and become vapor
- slow-moving particles in the vapor becomes part of the liquid
Effect of temperature on vapor pressure
- as temp. increases, average speed of particles increases
- so as temp. increases, equilibrium vapour pressure also increases
Define the enthalpy of vaporisation
A measure of the energy change when 1 mol of liquid converts to gas at standard pressure
What is the relationship between the boiling point of a liquid and the equilibrium of vapor pressure & atmospheric pressure?
The boiling point of a liquid is the temperature at which vapour pressure = atmospheric pressure
Elaboration: food in a pressure cooker is cooked faster because of the alteration in boiling point (70 degrees Celsius instead of 100)
mole
The amount of substance containing the same number of atoms as in exactly 12g of the isotope C-12
relative atomic mass
The average mass of an atom of the element, taking into account all the isotopes and their relative abundance, as compared to 1 atom of C-12
relative molecular mass
The sum of the relative molecular mass of all the atoms in a molecule
relative formula mass
The sum of the relative formula mass of all the atoms in one unit of an ionic compound
Difference between molecule and formula
Molecule: refers to covalent compounds
Formula: refers to ionic compounds
molecular formula
Gives the real number of atoms of the elements present in one molecule of the compound
empirical formula
The simplest whole number ratio of the atoms of elements in one molecule
Avogadro’s Law
an equal vol. of gases, both measured at the same temp. and pressure, contain an equal no. of particles.
v1/n1 = v2/n2
v: volume
n: no. of particles/moles
ideal gas concept
- no attractive forces between gaseous particles
- KE of particles are directly proportional to temp
- follows the kinetic particle theory 100%
when are real gases closest to the ideal gas concept?
when the temp is high and pressure is low
how temperature affects real gases
the lower the temp. is, the slower molecules move —> the stronger the intermolecular forces
how pressure affects real gases
the higher the pressure, the closer molecules are to each other —> the stronger the intermolecular attractive bonds
ideal gas equation
PV = nRT
P: pressure V: volume n: no. of moles R: ideal gas constant T: temp.
Boyle’s law
at constant temp , pressure is inversely proportional to volume
P1V1 = P2V2
gas law
P1V1 / T1 = P2V2 / T2
OR
PV/T = a constant
dilution of solutions equation
C/V = a constant OR c1v1 = c2v2 c = conc V = vol
solutions and concentration equation
conc. of soln x vol = amount of solute
mole equations
no. of moles = no. of particles / Avogadro’s constant
no. of moles = mass / molar mass
no. of moles = concentration x volume
law of conservation
matter can neither be created nor destroyed, it can only be changed from one form to another
how to calculate yield from reaction equations
- Obtain the stoichiometric values of the reaction (molar coefficients of each compound)
- Use mole equations to find the limiting reagent
- You can find the max yield from there
percentage yield formula
(experimental yield / theoretical yield) x 100
back-titration
- technique analysing excess acid/alkali after rxn is complete
- indirectly measures amount of limiting reactant
gas and molar volume relationship
- all gases under same conditions have same molar volume
e. g. STP/RTP
temperature
average energy of particles in a system
relationship between pressure and temp of gas
P/T = a constant
OR
P1/T1 = P2/T2
Charles’ Law
- volume is directly proportional to absolute temperature
- V/T = a constant
V1/T1 = V2/T2
why is beer stored in cold places?
- they can burst!
the higher the temp, the higher the pressure.
