Ethers due to absence of delocalized pair of electrons do not show resonance.

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$${C^*} = $$   asymmetric carbon
Number of optical isomers $$ = {2^n}$$
where, $$n = $$  number of asymmetric carbon atoms $$ = {2^1} = 2$$
Number of geometrical isomers $$ = {2^n}$$
where, $$n = $$  number of double bonds $$ = {2^1} = 2$$
Hence, total number of stereoisomers = Total optical isomers + Total geometrical isomers = 2 + 2 = 4

The strength of the acid increases with the inductive effect of the electronegative group attached to it ( $$-I$$  effect ). The strength of the acid decreases with the presence of electron releasing group.

[ Note : dipole moment is a vector quantity ].

Order of Acidic strength $$ \propto $$ stability of conjugate base.

Structure (B) is a $${3^ \circ }$$ carbocation, while (A) is $${2^ \circ }$$ and (C) and (D) are $${1^ \circ }$$ carbocations; thus (B) is the most stable.

$${\text{Heat of hydrogenation}} \propto \frac{1}{{{\text{Stability of alkene}}}}.$$

In $${C_3}{H_6}{O_3},$$   mass of 3 $$C$$ - atoms = 12 × 3 = 36
mass of 6 $$H$$ - atoms = 1 × 6 = 6
mass of 3 $$O$$ - atoms = 16 × 3 = 48
∴ Ratio of masses of $$C : H : O$$   is 36 : 6 : 48 or 6 : 1 : 8.
In $$HCHO,$$   mass of 1 $$C$$ - atom = 12
mass of 2 $$H$$ - atoms = 2
mass of 1 $$O$$ - atom = 16
∴ Ratio of masses of $$C : H : O$$   is 12 : 2 : 16 or 6 : 1 : 8.