Formulae, equations and amount of substance Flashcards
(32 cards)
What are moles
.The amount of substance that
.Contains the same number of particles
.as the number of carbon atoms
.in exactly 12g of 12C
What is the Avogadro constant
.Very large
.Approximatey 6.02 X10 power 23
What is the relative atomic mass
The weighted mean mass of an atom of an element compared to 1/12th the mass of 12C atom
What is the relative formulae mass
Calculated by adding together all Ar value for all the atoms present in a unit of a substance
What is molar mass
.Is the mass per mole of a substance
.has the units gmol-1
Whats the formulae for calculating moles
n=M/mr
What is a molecular formulae
Shows the actual numbers of atoms of each element in its molecules
What is the molecular formula for butane
C4H10
What is an empirical formulae
The simplest whole number ratio of the atoms of each element it contains
What’s the empirical formulae for butane
C2H5
How are organic compounds represented
Using structural formula
What is Avogadro’s law
It states that equal volumes of gases under the same conditions of temperature and pressure contain the same number of molecules
When does the volume of a fixed amount of gas increase
as the:
Temperature increases
Pressure Increases
What’s the molar mass of any gas
24.0dm3
What’s the ideal gas equation
What does each one stand for
Pv=nRT P=Pressure in pa V=volume in m3 n=amount of gas in mol R=gas constant 8.31 t=temeprature in K
Whats the formulae for concentration
C=m/vx1000
How do you convert cm3 —>dm3
divide by 1000
How do you convert dm3 to cm3
multiply by 1000
What is a titration
A method in which the volumes of two reacting solutions are measured so that the concentration of one of the solutions can be determined
What are the main steps of an acid-alkali titration
1) Use a pipette to transfer 25cm3 of alkali to the conical flask and added some indicator
2) Add acid from the burette to the flask until the endpoint is reached
3) Record the burrette reading before and after adding the acid
What is meant by the following words:
a) Meniscus
b) Endpoint
c) Titre
d) Concordant results
e) Equivalence point
a) The curve in the upper surface of the liquid
b) Where the indicator first changes color
c) The volume of solution added to reach the endpoint
d) When two or more titres are within 0.10cm3 of each other
e) Where the reaction is exactly completed
Give 5 tips for accurate results
1) Add only a few drops of indicator
2) keep the burette verticle
3) Add dropwise near the endpoint
4) Stop adding when the indicator first changes color
5) Record reading to 0.05cm3
What are the 4 steps you need to take for titration calculations
1) Calculate the mean titre of the titrant
2) Calculate the amount of solute in the titrant
3) Calculate the amount of solute in the analyte (unknown solution)
4) Calculate the concentration of the analyte
What needs to be selected in order to calculate mean titre
Two concordant results
add them together and divide by 2
