mod 2 Flashcards
What is the law of conservation of mass?
matter can not be created or destroyed only rearranged
mass(reactants) = mass(products)
what is the law of definite proportions?
certain compounds always contain the same elements in the same proportions by mass
What is a mole?
the mole concept was developed to easily talk about large numbers and is 6.022 x 10^23 atoms –> avagadros number, however they DO NOT weight the same
Equation for no. of moles
n = m(mass)/MM(molar mass, mass on periodic table)
What is a limiting reagant?
one substance that usually limits the reaction while the other is an excess
How to calculate the limiting reagent?
- make a balanced equation
- find the number of moles of all reagents
- based on molar ratio find the limiting one
- using the moles of the limiting one find the moles of the products (using molar ratio)
How to calculate empirical formula?
- assume that the compounds mass is 100g
- draw a table with the elements on top and mass, moles, divide by, ratio on the side
- find mass and moles
- divide them by the smallest no. of moles (limiting reagent)
- find ratio between each (must be to a whole number)
What is concentration?
refers to the amount of solute that is dissolved per unit of solvent
What is molarity? (most common measure of concentration)
is the number of moles of solute per litre of solution (mol-1/L)
formula: c = n(no. of moles)/v(volume in litres)
What is Dilution?
process to lower the concentration of a substance by adding more solvent, but keeping the solute unchanged (rearrange molarity formula)
What are the aspects associated with the gas laws?
pressure (kPa), temperature (K), volume (L), mass (g)
when two of these aspects are being addressed, it is assumed that the others remain at a constant
What is Boyle’s law?
pressure is inversely proportional to volume P = k/v
What is Gay-Lussac’s law?
pressure is directly proportional to temperature P = kT
What is Charles’ law?
volume is directly proportional to temperature v = kT
What is Avagadro’s law?
volume is directly proportional to no. of moles v = kn
FORMULAE SHEET: What is STP?
standard temperature and pressure: at 100kPa and 0C / volume = 22.71L
FORMULAE SHEET: What is RTP/SLC
room temperature and pressure: at 100kPa and 25C / volume = 24.79L
What is the Combined Gas Law?
combines charles, boyles and gays laws:
k (constant) = PV/T
What is the Ideal Gas Law?
PV = nRT
R (universal gas constant on FORMULAE SHEET)
What is stoichiometry?
deals with the quantitive relationship between reactant and products
the stoichiometric ratio is the ratio of the co-efficients of the equation’s elements
What is systematic error?
a constant error
- hard to detect
- affects accuracy
- from apparatus, environmental or parallax error
What is a random error?
a variable error
- easy to detect
- affects reliability
- can be minimised (NOT GOTTEN RID OF) by repeating experiment
what is ppm
parts per million measured in milligrams per litre
