Quantitative chemistry Flashcards
What is the equation to find the mole of a substance?
Moles = Mass of substance/Ar or Mr
Mass of substance must be in grams
Ar for elements
Mr for compounds
What is the Relative Atomic Mass and its symbol?
The Ar of an element is a weighted mean mass of the isotopes of an element compared with that of the C (12) Isotope, which has a mass of exactly 12.
What is the Relative Molecular Mass and its symbol
The Mr of a substance is the sum of the masses of all the atoms present in the formula of that element or compound. It is used when calculating the mass of a covalent compound.
What is the equation to find the Mass of a substance?
Mass = mole x Ar or Mr
Mass of substance must be in grams
Ar for elements
Mr for compounds
What is the concentration of a solution in grams?
The concentration (g/dm3) is the number mass of grams that is dissolved in 1m3 of a solution.
What is the equation to find the concentration of a substance in grams?
Concentration (g/dm3) = mass of solute (g) / volume (dm3)
What is the concentration of a solution in moles?
The concentration (mol/dm3) is the number of moles that is dissolved in 1dm3 of a solution.
What is the equation to find the concentration of moles a substance?
Concentration (mol/dm3) = moles / volume (dm3)
What are the three steps for carrying out a titration?
Preparing the burette
Preparing and rinsing the pipette
Carrying out the titration
What are the steps for preparing the burette when carrying out a titration?
- Rinse the burette with the solution it is to be filled with and discard the rinsings
- Fill the burette with solution
- Make that the jet is filled and that there is no air bubbles
- Record the volume at the bottom of thee meniscus at eye level
What is the equation for the conversion between the concentration in grams and in moles?
g/dm3 = mol/dm3 X Mr
How do you find the original concentration of diluted solutions?
original conc = conc X dilution factor
What are the steps for preparing the pipette when carrying out a titration?
- Rinse the pipette with solution to be placed in the conical flask
- Using a pipette filler, draw up solution until the meniscus meets the bottom of the pipette
- Release the liquid into the conical flask
- Touch the pipette on the surface of the liquid to remove the last drop
What are the steps when carrying out a titration?
( After the burette and pipette )
- Measure out a volume of solution (25cm cubed) using a pipette and a pipette filler, and place it in a conical flask
- Add a few drops of an indicator, such as methyl orange or phenolphthalein
- Add the other solution from the burette, swirling the contents of the conical flask until the indicator just changes colour.
- Read the volume delivered using the bottom of the meniscus at eye level, and record the value. Then repeat two more time accurately to find the average titre
Method for diluting a 25cm cubed solution to 250cm cubed?
- Wear eye protection
- Rinse a pipette with the solution to be diluted
- Pipette 25cm cubed of solution into a 250cm cubed volumetric flask
- Add deionised water until the bottom of the meniscus is on the line
- Stopper, invert and shake the flask to mix the solution
