Topic 5 - Formuale And Eqautions Flashcards
Definition of a mole?
The mole is the amount of substance in grams that has the same number of particles are there are atoms in 12 grams of carbon -12.
Definitions of relative atomic mass?
Relative atomic mass is the average mass of one atom compared to one twelfth of the mass of one atom of carbon-12.
Definition of molar mass (unit)?
Molar mass is the mass in grams of 1 mol of a substance and is given the unit of g/mol.
Explain what is meant by Avogadro constant?
There are 6.02x10^23 atoms in 12 grams of carbon 12. Therefore ‘one mole of any specified entity contains 6.02 x10^23 of that entity’.
Formula for No of particles?
No of particles = amount of substance (in mol) x Avogadro constant.
Definitions of empirical formula
An empirical formula is the simplest ratio of atoms of each element in the compound.
Definition of Molecular formula?
A molecular formula is the actual number of atoms of each element in the compound.
Application of the ideal gas equation?
The ideal gas equation applies to all gases and mixtures of gases. If a mixture of gases is used the value n will be the total moles of all gases in the mixture.
Equations for ideal gas?
pV=nRT
Pressure in Pa
Volume in m^3
Temperature in K
R = 8.314 J/K/mol
How do you calculate empirical formula?
- divide the amount of each element by its molar mass.
- Divide the answers by the smallest value obtained.
- If there is a decimal divide by a suitable number to make it into a whole number
State Avogadro law?
Under the same temperature and pressure, one mole of any gas would occupy the same volume.
How much volume does a gas occupy at room temperature and pressure?
24 dm^3
Why do different gas particles occupy the same volume?
The gas particles are very spread out hence individual differences have no effect.
What are the ideal ways in which gases behave?
a. They are in continuous motion
b. No intermolecular forces experienced
c. Exert pressure when they collide with each other or a boundary
d. No kinetic energy is lost in the collisions
What does concentrations of a solution mean?
It is the amount of solute dissolved in 1 dm^3 of solvent
What are the steps to prepare a standard solution?
- weight the solute using the weigh by difference method.
- In a beaker dissolve the solute using the solvent.
- pour solution into a volumetric flask
- Rinse the beaker using the solution and add it to the flask
- Add solvent to the flask carefully until it reaches the graduation line
- Mix the solutions thoroughly to ensure complete mixing.
What does percentage yield mean?
The efficiency of which reactants are converted into products.
What are the reasons for not obtaining 100% yield?
- Reactions may be at equilibrium
- Side reactions could happen
- Loss of products during separation and purification.
- The reactants may be impure
atom economy?
The proportion of desired products compared with all the products formed in the reactions
Which type of reactions has 100 % atom economy.
Addition reactions (two or more reactants are combined to form a product)
What does systematic error mean?
The same error appears in each measurement.
The error of mass measurement can be reduced by using which method?
Weighing by difference method.
what are spectator ions?
are the ions in an ionic compound that do not take part in a reaction.
what is the equation using molar volume?
24 (dm^3) = volume/amount in mol
what is molar volume?
the volume occupied by 1 mol of any gas
equation for mass concentration? (g/dm^3)
mass concentation = mass of solute/volume of solution in dm^3
What are standard solutions?
is a solution whise concentration is accurately known
what are primary standards?
are substances used to make a standard solution by weighing.
What is the equivalence point?
the point at which there are exactly the right amounts of substances to complete the reaction.
what is accuracy?
is a measure of how close values are to the accepted or correct value.
what is precision?
is a measure of how close values are to each other.
whats are random errors?
are errors caused by unpredictable variations in conditions.
what are systematic errors?
are errors that are constant or predictable,usually because of the apparatus used?
what are the measurements with one error?
-pippete
-measuring cylinder
temperature
-volumetric flask
what are the measurements with two errors?
- temperature change
- mass change
- change in volume with a burette
what are precipitation reactions?
are reaction in which an insoluble solid is one of the products.
what is a hazard?
a hazard is a substance or procedure that can has the potential to do harm
what are some typical hazards?
- toxic
- flammable
- harmful
- irritant
- corrosive
What is a risk?
this is the chance that harm will result from the use of a harzardous substance or a procedure.
how do we try to minimse the risks from hazards?
Irritant - dilute acid and alkalis- wear googles
Corrosive- stronger acids and alkalis wear goggles
Flammable – keep away from naked flames
Toxic – wear gloves- avoid skin contact- wash hands after use
Oxidising- Keep away from flammable / easily oxidised materials
What is relative isotopic mass?
-the mass of an individual atom of a particular isotope relative to 1/12 of the mass of an atom of Carbon-12 .
