Which of the following has the lowest boiling point? Which subshell can be found in all three shells of an? How many chain isomers are shown by CH10? How many electrons are being carried by an S-orbit? What is the name of the functional group in the R-OH organic compounds?

• n-butane: $C_4H_{10}$ (straight chain)
• 2-methyl butane: $C_5H_{12}$ (branched chain)
• 2-methylpentane: $C_6H_{14}$ (branched chain)
• n-pentane: $C_5H_{12}$ (straight chain)

Boiling point generally increases with molecular weight. Among compounds with similar molecular weights, branching decreases the surface area for intermolecular forces, leading to a lower boiling point.
Comparing the molecular formulas, n-butane ($C_4H_{10}$) has the lowest molecular weight. Therefore, it will have the weakest London dispersion forces and the lowest boiling point.

The correct option is a) n-butane.

II. Which subshell can be found in all three shells of an atom?

• For $n=1$ (first shell): only $s$ subshell ($1s$)
• For $n=2$ (second shell): $s$ and $p$ subshells ($2s, 2p$)
• For $n=3$ (third shell): $s$, $p$, and $d$ subshells ($3s, 3p, 3d$)

The $s$ subshell is present in the first, second, and third shells.

The correct option is b) s-orbital.

III. How many chain isomers are shown by CH10?

The formula "CH10" is likely a typo and should be $C_4H_{10}$ (butane) or $C_5H_{12}$ (pentane) given the options. Since option (b) 2 is circled, we will assume the question refers to $C_4H_{10}$.

1. n-butane: $CH_3-CH_2-CH_2-CH_3$ (a straight chain)
2. 2-methylpropane (isobutane): $CH_3-CH(CH_3)-CH_3$ (a branched chain)

There are 2 chain isomers for $C_4H_{10}$.

The correct option is b) 2.

IV. How many electrons are being carried by an S-orbital?

According to the Pauli exclusion principle, any single atomic orbital (including an $s$-orbital) can hold a maximum of two electrons, provided they have opposite spins.

The correct option is c) 2.

V. What is the name of the functional group in the R-OH organic compounds?

R-OH represents an alcohol.

The $-OH$ group is called the hydroxyl group. In multiple-choice questions, the class name "Alcohol" is often used to refer to the functional group in this context.

The correct option is a) Alcohol.