mod 2 Flashcards
what is stoichiometry?
refers to the quantities of chemicals involved in a chemical reaction and how these are calculated
why is stoichiometry important?
- know how much reactant is needed in a chemical reaction
- can predict how much each product will make
- know which reactant may be in excess
- know which is the limiting reagent that is preventing more of the product(s) from being made
what is molar mass (g)?
sum of Avg. atomic mass of each type of atom and how many there are in a chemical formula
no. of moles formula?
mass / molar mass or n=m/MM
what is the percentage composition of a compound?
% composition by mass = mass of element / mass of compound x 100
what is the empirical formula?
the empirical formula is the chemical formula of a compound expressed in its simplest whole ratio of elements
what is a molecular formula?
it’s a multiple of the empirical formula
multiple number = molar mass of compound / molar mass of empirical formula
what is the molarity formula?
concentration (M) = moles of solute / volume of solution
c = n/v
what is a solution?
a solution consists of a solute dissolved in a solvent
what is concentration?
concentration refers to the amount of solute dissolved in a solution
how can we measure concentration?
- % composition by mass or grams of solute per 100g of solution (%w/w)
- mass of solute per litre of solution i.e. grams per litre (g.L-1)
- moles of solute per litre of solution i.e moles per litre (mol.L-1) or molar (M)
what are less measures of concentration?
- percentage by volume (%v/v)
concentration = volume of solute in ML / volume of solution in ML x 100 - percentage mass/volume (%m/v)
concentration = mass of solute in g / 100ML of solution x 100
how can you use molarity?
- how many moles has been used in a chemical reaction with a solution
- what mass of a solute is needed to make a solution with a set concentration
what is a standard solution?
a solution is any solution whose concentration is known accurately
how can standard solutions be used?
- to manufacture chemicals
- to test other chemicals or materials
- to determine the concentration of other solutions by being used to react in water
what is a primary solution?
is a term given to a chemical that can exist in pure form so that the number of moles can be accurately calculated from its measured mass
how can you use molarity in dilution?
- no. of moles before dilution = no. of moles of sample after dilution
- concentration = moles. of solute/volume of solution
- C1V1 = C2V2
what is titration?
a technique to determine the concentration of a solution (analyte) by reacting small volumes of it with a known volume of a standard solution (titrant)
what makes a good primary solution?
- can be stored without deteriorating or reacting with the atmosphere
- doesn’t absorb water from the atmosphere
- high molar mass to minimise error in measurement
how to analyse titration volume
- write balanced equation for reaction in conical flask
- calculate moles of standard solution
- n = c x v
- use mole ratios in the balanced equation to calculate the unknown test solution
- calculate the concentration of the test solution - c = n/v
particle kinetic theory
particles of a gas are far apart and exert no force of attraction on each other; instead they have a large amount of kinetic energy and zoom past each other
corollary of particle kinetic theory
- gases occupy the full volume of their container
- gases are compressible
- gases have low density
what is gas pressure?
the amount of force per unit surface area is measured when gas particles hit the floor, walls and lid of their container when they exert a force
formula for gas pressure?
pressure = force/area
1 bar = ?
= 100 000 Pa = 100 kpa
1 newton of force per square metre = ?
= 1 pascal (Pa)
1 atmosphere (atm) = ?
= 760 mmgh = 101.3 kpa
what is Boyle’s law
pressure is inversely propotion to volume for a gas at constant temperature
- as the pressure decreases, the volume increases and vice versa
boyle’s law formula?
P1V1 =P2V2
what is charle’s law?
volume is indirectly proportional to temperature for a gas at constant pressure
- as the temperature of a gas decreases, the volume of the gas decreases
- vice versa
charle’s law formula?
v1/t1 = v2/t2
what is Gay-Lursac’s law?
pressure is directly proportional to temperature (in K) for a gas at constant volume
- as the temperature of a gas is decreased, the pressure of the gas decreases
- vice versa
Gay-Lursac’s formula?
p1/t1 = p2/t2
