help with syllabus point!!!! (1 Viewer)

[poopoohead]

Identify a range of salts which form acidic, basic or neutral solutions, and explian their acidic, neutral or basic nature

Im a little confused

ok- I know that a strong base + strong Acid = neutal salt

Im a bit confused on why this is the case:

Is it because a) anions/cations of strong acids/bases tend to undergo little or no ionisation- thus resulting in neutral salt- They do not undergo hydrolysis???

(by the way- what is hydrolysis)

OR

is it b) because of complete ionisation, there is no reverse reaction producing H+ or OH -

OR

c) some other reason which will confuse me even more

any one spare a moment from studying for trials to lend a hand?

thank you and goodluck (in unconfusing me and in ur trials)

regards- poopoohead

 

[priesty]

Below are some of my notes on this specific dot point. Hopefully they will clear up you uncertainties.


4.2.4 Identify a range of salts which form acidic, basic or neutral solutions and explain their acidic, neutral or basic nature

• A salt is an ionic compound containing a cation other than H+ & an anion other than OH- or O2- (e.g. KNO3, MgCl2, Na2SO4)
• Another way of thinking of salts is to consider them as being formed by the replacement of hydrogen in an acid by a metal ion or NH4+
o Salts from HCl  Chlorides
o Salts from H2SO4  Sulfates
o Salts from HNO3  Nitrates
o Salts from H2CO3  Carbonates

• In dilute aqueous solutions salts are dissociated into ions Mg(NO3)2  Mg2+ + 2NO3-
• Many salts do not form neutral solutions because the ions react with water to produce H+ or OH-

1. Neutral anions are derived from strong acids e.g. Cl- does not react with water to produce HCl or OH-

2. Neutral cations are group 1 or 2 cations and are derived from strong bases (NaOH)

3. Basic Anions are derived from weak acids and react with water to produce OH-
e.g. CH3COO- + H2O  CH3COOH + OH- ~ only slightly basic

4. Acidic Anions (e.g. HSO4-) are derived from multiprotic acids like H2SO4. They contain hydrogen atoms, which can be transferred to water molecules
HSO4- + H2O  H3O+ + SO42-
(Note: HCO3- & HPO42- are basic)

5. Acidic Cations are derived from weak bases & aquated metal ions e.g. NH4+ is derived from the weak base NH3
NH4+ + H2O  NH3 + H3O+ ~ only slightly acidic

Predicting Salt Solutions
• Consider the cation & anion and whether thy react with water

e.g. NaCl
Both Na+ and Cl- do not react with water so is neutral

KCH3COO
K+ does not react therefore it is basic as CH3COO- reacts

Summary
•A salt formed by a strong acid and strong base is NEUTRAL
o NaCl – Acid: HCl Base: NaOH
•A salt formed by a strong acid and a weak base is ACIDIC
o NH4Cl – Acid: HCl Base: NH3
•A salt formed by a weak acid and a strong base is BASIC
o CH3COONa – Acid: CH3COOH Base: NaOH

 

[poopoohead]

thank you

 

[tristambrown]

easy ones to remember

NaCL (table salt ) - NEUTRAL salt (from strong acid HCL)

NaHSO4 (ionises to form sulfuric acid ) salt known as Pool shock made from diprotic acid H2SO4 ----- ACIDIC SALT


NaHCO3 - Sodium Bicarbonate (baking soda) - BASIC SALT - reacts with water to form OH- and reform original acid equilibrium ( from diprotic Carbonic Acid)

 

[Naylyn]

That is the best explaination of the Ph of salts that I have ever heared, it makes so much more sense that way than the way that my textbook tries to explain it.

 

[priesty]

no worries guys

 

[xiao1985]

*stuns in horror

that response came with a lag of 3 months Oo
gratz on hsc, and look forward to see an other science nerd in USyd ^^