Acids And Bases Flashcards
Define acid (Arrhenius theory)
A neutral molecule which dissociates in water to form a hydrogen ion and an anion
Define base (Arrhenius theory)
Dissociates in water to form a hydroxide ion and a cation
Strong acids and bases(Arrhenius)
Dissociates fully in aqueous solutions
Weak acids and bases (Arrhenius)
Only dissociates slightly in aqueous solution
Conductivity of weak acids(Arrhenius)
Weak acids conduct poorly because few ions
Conductivity of strong acids
Strong acids conduct well because there are numerous ions
Limitations of Arrhenius theory
Limited due to dilute aqueous solutions and has been superseded/ amphoteric substance not explained (water not amphoteric)
Acid (Bronsted-Lowry theory)
Acid is a proton donor
Base ( Bronsted-Lowry theory)
Base is a proton acceptor
Strength of acids(Bronsted-Lowry)
Stronger acids more readily donates a proton
Conjugate acid-base pairs
Species that differ from each other by H+
The strength of an acid if it’s conjugate base is weak
The stronger the acid the weaker the conjugate base
Indicator
Substances that changes colour with pH or at the end-point of a titration
Define Conjugate acid
Produced by a gain of one h+
Amphoteric
It can act as both a Brønsted-Lowry acid and a Bronsted-Lowry based.
Neutralisation
the reaction betweem acid and a base to form salt and water.
Alkali
a base that is soluble in water.
Mono basic acids
Produces one H+ ion in solution
Dibasic acids
Produces two H+ ions in solution
Tribasic acids
Produces three H+ ions in solution
Dissociation
When acids are places in solutions they split up into their ions, hydrogens ions and anions
Salts
Formed when the H+ of the acid is replaces by a metal ion
Limitation of ph scale
Accurate only for dilute solutions
pH
-log10[H+]
How to test sample of mineral water for presence of the sulfate ion
Add barium chloride( BaCI2) / white insoluble in HCI remains after addition of HCI when sulfer present
Explain the term standardised
Concentration found by another titration
State a precaution when end point in sight
Add drop by drop, swirl conical flask and wash down sides of conical flask.
Describe how the liquid level in burette was adjusted to zero mark.
Fill above mark and adjust slowly with tap
Name a primary standard reagent to standardise the HI solution?
Anhydrous sodium carbonate (Na2COs)
Why is sodium carbonate a primary standard yet sodium carbonate crystals are not?
Sodium carbonate is anhydrous where as sodium carbonate crystals are hydrated. Primary
standards are anhydrous
Why is it necessary to dilute vinegar?
To prevent excess amount of sodium hydroxide being used
Purpose of white tile?
To see colour change more clearly.
Purpose of swirling conical flask?
To ensure mixing of chemicals
What are the two purposes of Sulfuric acid
- To prevent oxidation of Fe2+ to Fe3+
2. To ensure an acidic medium to reduce Mn0+-
Why is there never an indicator when potassium permanganate is used?
Potassium permanganate is its own indicator
How is iodine brought into aqueous solution?
By reacting iodine with potassium iodide we form potassium triiodide which when dissolved in water simply forms triiodide (soluble).
Why is excess potassium iodide used?
Anything “excess” is to ensure all of reactant has reacted/ also to keep iodine in solution.
What indicator is used for sodium thiosulfate?
Starch. It is added when pale yellow colour formed. Goes blue-black to colourless
Why is distilled water better than deionised water for experiments?
Distilled water contains no chlorine oxidising agents. It is purer than deionised water.
Name a primary standard reagent used to standardise potassium permanganate?
Ammonium iron (Il) sulphate.
