All Units Flashcards
What is Gravimetric Analysis?
Discovering the mass of a chemical that is isolated from a mixture or precipitated in a reaction
2 common examples of an appropriate time to use Gravimetric Analysis
Percentage of water in bread Concentration of salt in baby food
What is the sign that the Gravimetric Analysis has reached its end?
The measured mass is constant
What does a desiccator do?
Absorbs moisture
When measuring the mass of the precipitate, what do you have to consider?
The degree of solubility of the compounds
How do you calculate the mass of the product precipitate?
Step 1: Balance equation
Step 2: calculate mol of the compounds mass you are given
Step 3: Use ratios to work out the mol of the compound whose mass you are trying to work out
Step 4: n=m/GFM
Step 5: If percentage is required final/initial mass x100
What is volumetric Analysis?
A process using volumes of liquids to analyse a concentration (basically titration)
What is a primary standard solution?
A substance so pure that the amount of substance, in moles, can be calculated accurately from their masses
List 4 possible characteristics of a primary standard solution
- Readily available 2. Available in pure form 3. Not readily react in the atmosphere 4. Be easily stored 5. Have high molar mass 6. Be inexpensive
Give three examples of primary standard solutions
- Sodium carbonate 2. Sodium borate 3. Hydrated oxalis acid
What formula is likely to be used when calculating volumetric analysis?
C1V1= C2V2
Describe the process of preparing a standard solution
- Work out mass needed - Dissolve the weighed sample in a small beaker and transfer to the volumetric flask - wash the small beaker at least three times and add to flask - half fill the water, shake to dissolve sample - add water up to the calibration line then shake again
Why aren’t common acids generally used as standard solutions?
Often absorb water in the atmosphere when they react with CO2, leaving them impure or have unknown exact concentration
In titrations, what is meant by Aliquot and equivalence point?
Aliquot - volume measured out by the pipette
Equivalence point - the point in the reaction which the reaction is just complete (the reactants are in their exact mole proportions)
Name the four types of volumetric analysis
- Acid base (neutralisation) 2. Redox 3. Back titration 4. Complexometric titrations
What does %w/w , %v/w mean?
Percentage of : weight in weight and volume in weight
How do you calculate ppm?
What is a weak acid?
A weak acid is an acid which partially dissociates in solution
Describe a back titration
Stage 1- Reactant A of unknown concentration is reacted with excess reactant B of known concentration Stage 2- A direct titration is then performed to determine the amount of reactant B in excess
When do we use back titrations?
-A reactant is volatile -Acid or base is insoluble -A particular reaction is slow -The end point is very difficult to observe if you use a weak acid or base
What is light?
Light is waves of energy which consists of photons
Equation to find the speed of light where; speed of light= c, frequency=v and wavelength=λ
c=λv
Equation of wave number
Equation for frequency
- v=vc
Equation for energy of a photon
E=hv
Energy for one mole of a photon
E=Lhf
When does the continuous spectrum occur?
When visible light passed through a glass prisim
When does the emission spectra occur?
When electrical energy is passed through a gaseous sample, consists of narrow lines of colour
What are excited electrons?
Electrons with a high amounts of energy. These electrons jump between energy levels and once they fall back to the ground state light is emitted
What is the emission spectra?
The different wavelengths of light that are produced when elements release energy
Which parts of the electromagnetic spectrum can emission lines be detected?
In both UV and infrared
How do you calculate the wavelength of any line?
1/lamda=R(1/n21 - 1/n22)
From the wavelength equation, what does n1 equal when dealing with a line in the Lyman series?
1
From the wavelength equation, what does n1 equal when dealing with a line in the Balmer series?
2
What is the infinity level?
The highest possible energy an electron can have as part of an atom
What is lambert’s law?
A=Elc
What does each of E,l and c refer to in Lamberts law?
E= Epsilon l=length of solution the light passes through c= concentration of solution
What does Heisenberg’s Uncertainty Principle state?
You cannot determine the position and momentum of an electron at the same time
What does Aufbau’s Principle state?
Electrons enter at the lowest available energy level
What does Pauli’s Exclusion Principle state?
No two electrons can have the same four quantum numbers
What does Hund’s Rule of Maximum Multiplicity state?
When in orbitals of equal energy, electrons will try to remain unpaired
What is an orbital?
A region of space where one is likely to find an electron
What shape and occurrence is seen with the orbital s?
Spherical and one in every principal level
What shape and occurrence is seen with the orbital p?
Dumb-bell and three in level 2 upwards
What shape and occurrence is seen with the orbital d?
Various shapes and seen 5 times in level 3 upwards
What shape and occurrence is seen with the orbital f?
Various and seen seven times in level 4 upwards
Which significant orbital over laps another?
4s overlaps 3d
Which elements are exceptions to the configuration rules and why?
Chromium and copper To achieve a more stable arrangement of lower energy, one of the 4s electrons is promoted into the 3d to give six unpaired electrons.