What are standard solutions
Standard solutions are solutions with accurately known concentrations. It can be used to determine the concentration of another reagent.
Exception: NaOH
NaOH is deliquescent and it absorbs water or CO2 readily in air
How to obtain insoluble salt
- Dissolve solid xx in water
- Then mis with excess yy solution
- Filter the mixture to obtain the solid residue zz
- Wash it with deionized water and then dry in oven
How to obtain soluble crystal
- Dissolve excess solid xx in dilute yy
- warm and stir the mixture gently with a glass rod
- Remove the excess solid xx by filtration using filter funnel and filter paper
- Evaporate the filtrate to obtain a saturated zz solution
- Cool the concentrated zz solution to obtain crystals
- Filter the crystals and wash the crystals with a little cold distilled water
- Dry the crystal in oven
Dilution
- Pour a small amount of the conc. xx acid to a large amount of water and keep stiring
- Wear goggle
Why should we pour conc.acid/akali into large amount of water
Dilution is a highly exothermic process.
The heat evolved may cause the acid/alkali to splash out
How to measure pH value
pH paper/ universal indicato/ pH meter
What are the factors affecting pH value
- [H+]
- basicity
- strength
show xxx is a weak acid/alkali
Measure the pH value/ electrical conductivity/ enthalpy change of neutrallisation/ temperarture rise in neutralization
Fair comparison
e.g. same concentration of xxx and yyy
How to prepare burette
- rinse the burette with distilled water then with the xx acid
- fill the burette with xx acid
- Make sure that the space between tap and tip of burette is filled with the xx acid
** two decimal places for burette value!!!!!
How to prepare Conical flask
- Rinse with distilled water
- Add indicator
How to prepare Volumetric flask
- Rinse with distilled water
How to prepare xxx cm3 solution?
Transfer the solution to a xxx cm3 volumetric flask using pipette
Add distilled water to the flask until the bottom of the meniscus reaches the graduation mark.
Why is concentrated acid/ alkali not suitable for performing titration?
The reaction of conc HCl and NaOH is highly exothermic.
The solution may spill out and cause accidents.