Formulae And Amounts Flashcards
Calculate moles when mass is given
Moles= mass/molar mass (RFM)
Calculate moles in a solution
Moles = concentration x volume
Calculate moles in gas at room temperature and pressure
Volume = moles x 24
Cm3 into dm3
Divide by a 1000
Calculate gas at any temperature or pressure and give the SI units for each component also known as ideal gas equation
PV=nRT Pressure in pascals (kPax1000) Volume in dm3 N=number of moles R=8.31 T=temp in Kelvin (Celsius plus 273)
Avagado calculations
Moles x 6.02x10 to the power of 23 = number of molecules
Empirical formula table headings (vertically)
Horizontally is the elements Mass or % RFM Moles Divide by the smallest Ratio
Combustion analysis
😓
General procedure for mole calculations
Balanced equation Write what you know under each species Convert to moles where possible Use molar ratio (stoichiometry) to find where you’re going Convert into asked units
Find molecular formula
Empirical formula mass then divide by given mass and multiply each element in compound by the scale factor
Mole definition
Amount of substance that contains the same number of particles as 12g of Carbon - 12 isotope
Mass concentration equation
Mass of solute divided by volume of solvent
Molar concentration equation
Rearranging concentration x volume = moles to get concentration = moles divided by volume
What is a standard solution?
A solution whose concentration is accurately known.
What are primary standards?
Substances used to make a standard solution by weighing.
Primary standards criteria:
Solids with high molar masses High purity Chemically stable React rapidly and completely with other substances used in titrations To abosorb water from the atmosphere
Apparatus for making primary solution of sulfamic acid
Accurate balance Weighing bottle Spatula 250cm3 beaker and volumetric flask Deionised water Funnel Glass stirrring rod
How to prepare a primary solution of sulfamic acid
Add approximately 2.5g of sulfamic acid to the weighing bottle and record measurement then transfer acid to a beaker and weigh bottle again. Add 100cm3 of deionised water to beaker until all sulfamic acid is dissolved and stir with rod. Use deionised water to wash all traces of acid from rod into beaker. Then place funnel in volumetric flask and pour solution from beaker. Rinse the inside of the beaker several times and transfer findings to flask. Add deionised water to flask and make it up exactly to the graduation mark. Put stopper and invert half a dozen times to make a uniform solution.
What is the aim of titration
Measuring the volumes of two solutions that react together can also be known as volumetric analysis
Titration method
Rinse the conical flask with deionised water on a white tile
Use a pipette fillers and rinse the pipette with deionised wafer and then with some of sodium hydroxide
Use the pipette to transfer 25cm3 of sodium hydroxide to the conical flask
Add three drops of methyl orange
Rinse the burette with deionised water and then with some sulfamic acid solution
Fill burette with sulfamic acid and set it up above the conical flask
Record initial burette reading
Add sulfamic acid to the conical flask until the indicator just changed colour and again record burette reading
Empty and rinse conical flask with deionised water and repeat till concordant titres are obtained
Concordant titres
Each with thing 0.1cm3 of each other and all together 0.2cm3
Methyl orange colour changes and works well with what combinations of acids and bases
Red in acid
Yellow in alkali
Pink in neutral
Strong acid weak bade
Strong acid strong base
Phenolphthalein colour changes and acid base combinations
Colourless in acid
Pink in alkali
Weak acid strong base
Strong acid strong base
Examples of strong acids are:
HCl
HNO3
