List five common uses of acids and bases in our daily lives.

Step 1: Lewis acid definition
A Lewis acid is a substance (atom, ion, or molecule) that can accept a pair of electrons to form a coordinate covalent bond. A Lewis base is a substance that can donate a pair of electrons.

Step 2: Common inorganic and organic Lewis acids
Inorganic Lewis acids: $BF_3$, $AlCl_3$, $BeCl_2$, $Fe^{3+}$, $H^+$, $SO_3$.
Organic Lewis acids: carbocations like $CH_3^+$, $(CH_3)_3C^+$, acyl chlorides like $CH_3COCl$.

Step 3: Lewis acids and bases in daily life
Lewis acids: $CO_2$ (in carbonated drinks, accepts electrons from water), $SO_2$ (in pollution, from burning coal).
Lewis bases: $NH_3$ (in household cleaners), $OH^-$ (in soaps).

Step 4: Lewis structures for the acids
HNO$_3$: Central N bonded to one OH (single bond), one =O (double bond), one O$^-$ (single bond, resonance). N has 8 electrons (one from charge).

(with lone pairs: O in OH has 2, =O has 2, terminal O has 3; resonance forms).

H$_2$SO$_4$: Central S bonded to two OH (single), two =O (double). S has 12 electrons (expanded octet).

HClO: H--O--Cl, O has 2 lone pairs, Cl has 3 lone pairs.
$H--O--Cl \quad (: on O and Cl)$

HBr: H--Br, Br has 3 lone pairs.
$H--Br:$

HClO$_4$: Central Cl bonded to three =O, one OH. Cl has 12 electrons.

(resonance, all O equivalent).

Step 5: Lewis structures for NH$_4^+$ and H$_3$O$^+$
NH$_4^+$: Central N with 4 N--H single bonds (8 electrons on N).
[H--N--H \atop | \atop H-- --H]^+

H$_3$O$^+$: Central O with 3 O--H bonds, 1 lone pair on O.
[H--O--H \atop | \atop H]^+ \quad (: on O)

Step 6: Formulas for conjugate bases
Formula first: Conjugate base = acid $-$ H$^+$.
HClO$_4 \to$ ClO$_4^-$.
$\ce{HClO4 ->[ -H^+ ] ClO4^-}$
H$_2$SO$_4 \to$ HSO$_4^-$.
$\ce{H2SO4 ->[ -H^+ ] HSO4^-}$
HNO$_3 \to$ NO$_3^-$.
$\ce{HNO3 ->[ -H^+ ] NO3^-}$

Step 7: Formulas for conjugate acids
Formula first: Conjugate acid = base $+$ H$^+$.
ClO$_4^- \to$ HClO$_4$.
$\ce{ClO4^- ->[ +H^+ ] HClO4}$
SO$_4^{2-} \to$ HSO$_4^-$.
$\ce{SO4^2- ->[ +H^+ ] HSO4^-}$
NO$_3^- \to$ HNO$_3$.
$\ce{NO3^- ->[ +H^+ ] HNO3}$

Step 8: Amphoteric and amphiprotic substances
Amphoteric (act as both Lewis acid and base): $\ce{Al(OH)3}$, $\ce{Zn(OH)2}$, $\ce{Sn(OH)2}$.
Example: $\ce{Al(OH)3 + OH^- -> Al(OH)4^-}$ (accepts e$^-$ pair, Lewis acid); $\ce{Al(OH)3 + 3H^+ -> Al^3+ + 3H2O}$ (Lewis base).

Amphiprotic (act as both Brønsted acid and base): $\ce{H2O}$, $\ce{HCO3^-}$, $\ce{HSO4^-}$.
Example: $\ce{H2O + HCl -> H3O^+ + Cl^-}$ (acid); $\ce{H2O + NH3 -> NH4^+ + OH^-}$ (base).

Step 9: Sulfur atom in SO$_2$ as Lewis acid
Lewis structure of SO$_2$: Central S with 1 lone pair, double bond to one O, single bond to other O (resonance, 10 electrons on S).

S has incomplete octet (can accept e$^-$ pair), so SO$_2$ is Lewis acid (e.g., forms adduct with amines).
This explains corrosion in pipes: SO$_2$ from pollution accepts electrons from metal oxides, breaking layers.

ClO_4^-, HSO_4^-, NO_3^-

HClO_4, HSO_4^-, HNO_3