5.3 [Concentrations of solutions, Preparing a standard solution and titration] Flashcards
How is mass concentration calculated?
Mass concentration in gdm3 = Mass of solute/Volume of solution.
What is the equation for molar concentration?
Concentration = Amount (mol)/ Volume
or
Moles = Concentration x volume
Units dm-3
How are concentration and mass equations use to calculate molar concentration?
First calculate the number of moles using one of the equations. Then place into the ratio and x by the element which need to find the mass for.
What is a solute?
A solute is something that is dissolved
What is a solvent?
A substance that is dissolved in a solute.
What is a solution?
A solution is a solute dissolved in a solution.
What is mass concentration?
The mass concentration of a solution is the mass of the solute/ by the volume of the concentration
What is a standard solution?
A standard solution is a solution whose concentration is accurately known. One way to prepare a standard solution is to take a known mass of a substance and dissolve it in water to make a known volume of solution.
What are the features of standard solutions?
Be solids with high molar mass
Be available in a high degree of purity
Be chemically stable
Not absorb water from the atmosphere
Be soluble in water
React rapidly and completely with other substances when used in titrations
How is a standard solution of Sulfamic acid made?
Available for primary standard solution in acid- base titrations that has necessary characteristics.
Need to calculate how much to weigh using the eq. n= c x then times the amount of substance by the Mr of sulfamic acid.
What is the method for preparing this standard solution?
Add 2.3g of sulfamic acid transfer to weigh bottle
Transfer into clean beaker and reweigh the weighing bottle
Add 100cm3 of deionised water to the beaker and stir till acid is dissolved
Remove stirring rod wash traces of solution from rod.
Place funnel in neck of volumetric flask and pour solution from beaker into the flask
Rinse the beaker inside several times and transfer rinsing to the flasks
Add deionised water to the flask and make up to graduation mark
Stopper the flask invert it to make uniform solution.
What is a titration?
Practical method with the aim of measuring the volumes of 2 solutions that react together and using the results to calculate the concentrations of one of the solutions.
What is the outline of the titration method?
Add the acid to the alkali until the equivalence point of the titration and the end point of the indicator is reached
Record the lowest part of the meniscus
Record the titre
Repeat the titration until concordant titres are obtained.
What is the method for the titration?
Rinse conical flask with deionised water place in white tile.
Using a pipette filler rinse the pipette with
deionised water and then with some sodium hydroxide solution
Use the pipette to transfer 25.0cm3 of the sodium hydroxide solution to the conical flask
Add 3 drops of methyl orange
Rinse burette with deionised water and then with some of the sulfamic acid
Fill burette with sulfamic acid solution solution and then set it up with the stand above the conical flask
Record the burette reading
Add sulfamic acid solution to conical flask until the indicator just changes colour and record the burette reading.
Rinse flask with deionised water
What are the 2 indicators used for titrations?
Methyl orange
Phenolphthalein
