Q.Assertion (A): Formaldehyde molecule has a planer geometry.
Reason (R): Carbon present in it is sp³ hybridised.

Formaldehyde is planar (A true), but the carbon is $sp^{2}$ hybridised, not $sp^{3}$ (R false). Correct option: (iii).

Concept. In methanal, $\text{H}_2\text{C}=\text{O}$, the carbonyl carbon forms three $\sigma$-bonds (two C–H and one C–O) and one $\pi$-bond. Three $\sigma$-bonds + one lone-region-free geometry means three electron domains $\Rightarrow$ $sp^{2}$ hybridisation, trigonal planar, bond angles $\approx 120^\circ$.

Analysis of the statements.

• Assertion: "Formaldehyde has planar geometry" — TRUE. All four atoms lie in one plane. …

Formalin is the common name for an approximately 40% w/v aqueous solution of formaldehyde, used as a disinfectant and biological preservative.

Formaldehyde (methanal, HCHO), the simplest aldehyde, is a gas at room temperature and is commercially supplied and used as a 40% aqueous solution called formalin. Formalin is used to preserve biological specimens, …

Formalin is the common name for an approximately 40% aqueous solution of formaldehyde (HCHO), used as a preservative and disinfectant.

Formaldehyde (HCHO), the simplest aldehyde, is a gas at room temperature and is commercially sold and used as an aqueous solution. A 40% solution of formaldehyde in water is given the trade name 'Formalin'. Formalin is widely used to preserve biological/anatomical specimens, as a disinfectant, and in the manufacture of Bakelite and o …

Formalin = 40% aqueous formaldehyde (HCHO); used to preserve biological specimens.

Concept. Formaldehyde (methanal, HCHO) is a gas at room temperature and is handled as its aqueous solution.

Definition & use. Formalin is a roughly 40% (by mass) aqueous solution of formaldehyde. Its main uses are as a preservative for biological/anatomical specimens and as a disinfectant; it is also used in …