(a)The molecular formula of propane is $C_3{H}_8$.

(b)The IUPAC name is 1-bromoethane .

The given statement is true.

For (A), the word propane refers to a compound composed of three carbon atoms joined by a single bond.
For (B): The numbering will begin at this carbon since there is just one substituent group (Br) in this molecule.

The prefix "prop" and the suffix "ane" are used to identify (A)propane.
-
Three carbon atoms are referred to as "prop," one bond is referred to as "ane," and the compound is a saturated molecule.
-
So let's attempt to create this compound's structure immediately. As follows:

Three carbon atoms make up this molecule, whereas eight hydrogen atoms make it up. Therefore, its molecular make-up would be $C_3{H}_8$.

(B) This structure consists of two carbon atoms joined by a single bond. A Br atom is joined to one of the carbon atoms. Here, a two-carbon chain is the maximum possible length for a carbon chain. But just now, we must choose the carbon from which to begin the counting.
As can be seen, the Br atom serves as the only substituent. Other functional groupings are not present. Additionally, while counting carbon atoms, the carbon closest to the substituent group or the carbon with the most prior functional group or substituent group comes first. Therefore, the carbon with the Br atom attached will be given the number 1.

Thus, this substance will be known as 1-bromoethane and have the chemical formula $C_2{H}_{5}Br$.
It is a volatile chemical with an ether-like odour and goes by the common name ethyl bromide. A molecule of ethene reacts with HBr to create it. Its preparedness response is going to be:

${\mathrm{H}}_2\mathrm{C}={\mathrm{CH}}_2+\mathrm{HBr}\to {\mathrm{H}}_3\mathrm{C}-{\mathrm{CH}}_2\mathrm{Br}$

Hence, the given statement is true.