Question

can you explain to me and provide examples 1) identifying and ranking the strongest acid or base.
2) predicting the direction of equilibrium in an acid base reaction
3) nomenclature of chiral molecules- including the halogen substituents
4) Determining R and S configuration

Answer 1

An acid is any substance that donates a proton (H^+ ion)

A base is any substance that accepts a proton (H^+ ion)

This leads to many interesting implications, one of which points to water acting as both and acid and a base, depending on the situation.

But back to your question! A strong acid according to the Bronsted-Lowry theory is one that donates pretty much 100% of it’s available protons, that is, it completely dissociates.

A strong base would accept it’s maximum amount of protons, again completely dissociating to provide hydroxide ions for the matching up with Hydrogen ions (protons).

Just a side note: some chemists actually consider bases to a neutral

Examples of strong acids are HCl, H2SO4, HI, HNO3 and HBr.

Examples of strong bases are NaOH, CaOH, LiOH and KOH.

Here are some general guidelines of principles to look for that can help you address the issue of acidity:
First, consider the simplified general equation of a simple acid reaction:

• The more stable the conjugate base, A-, is then the more the equilibrium favours the product side (Ka > 1), i.e. more dissociation of H-A
• More dissociation of H-A then the stronger H-A is as an acid, or
• The more the equilibrium favours products, the more H+ there is....
• The more H+ there is then the stronger H-Ais as an acid....
• So looking for factors that stabilise the conjugate base, A-, gives us a "tool" for assessing acidity.
• The larger Ka implies more dissociation of HA and so the stronger the acid.
• The larger Ka is, the more negative the pKa so the lower the pKa, the stronger the acid.

Electronegativity. When comparing atoms within the same row of the periodic table, the more electronegative the anionic atom in the conjugate base, the better it is at accepting the negative charge.

HI > HBr > HCl > HF

Size. When comparing atoms within the same group of the periodic table, the easier it is for the conjugate base to accommodate negative charge (lower charge density). The size of the group also weakens the bond H-X (note this trend should be applied with care since it only works within a group).

Basicity
A convenient way to look at basicity is based on electron pair availability.... the more available the electrons, the more readily they can be donated to form a new bond to the proton and, and therefore the stronger base.

Electronegativity. When comparing atoms within the same row of the periodic table, the more electronegative the atom donating the electrons is, the less willing it is to share those electrons with a proton, so the weaker the base.

F-> Cl- > Br- > I- Size. When comparing atoms within the same group of the periodic table, the larger the atom the weaker the H-X bond and the lower the electron density making it a weaker base.RO- >RCO2- Resonance. In the carboxylate ion, RCO2- the negative charge is delocalised across 2 electronegative atoms which makes it the electrons less available than when they localised on a specific atom as in the alkoxide, RO-.

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