# Which of these designates a gas at room temperature?

## A) $\text{HCl} \left(g\right)$ B) $\text{Br"_2(l)"/""alcohol}$ C) ${\text{C"_(12)"H"_(22)"O}}_{11} \left(a q\right)$ D) ${\text{Cl"_2(g)"/""CCl}}_{4} \left(l\right)$

Jan 14, 2017

$\text{HCl} \left(g\right)$, as $\text{HCl}$ is naturally a gas at room temperature and pressure. It boils below room temperature, at $- {85.05}^{\circ} \text{C}$.

The way you can figure out what you're looking at is by looking at what is in parentheses:

• $\left(g\right) = \text{gas}$
• $\left(l\right) = \text{liquid}$, or very concentrated (high $\text{mol solute"/"L solution}$)
• $\left(s\right) = \text{solid}$, or precipitate if within a reaction

The above are all phases, though $\left(l\right)$ can indicate a concentrated solution.

Anything else specifies a solvent that the solute dissolves in (or a liquid that another liquid mixes with to form a liquid-liquid mixture), which is another way of saying that it is a solution:

B) specifies bromine liquid (${\text{Br}}_{2} \left(l\right)$) dissolved in liquid alcohol (bromine is a liquid at room temperature and pressure). An alcohol can be anything containing only $\text{C}$ connected to $\text{H}$ (a hydrocarbon end), and $\text{OH}$ (a hydroxyl group), such as ethanol and butanol.

C) is sucrose (common sugar, ${\text{C"_(11)"H"_(22)"O}}_{11}$) dissolved in water. $\left(a q\right)$ denotes an aqueous solution, which is by definition something dissolved in water.

D) is chlorine gas (${\text{Cl}}_{2} \left(g\right)$) dissolved in carbon tetrachloride liquid (${\text{CCl}}_{4} \left(l\right)$). Chlorine is a gas at room temperature (check that its boiling point is less than ${25}^{\circ} \text{C}$), while ${\text{CCl}}_{4}$ has a boiling point higher than ${25}^{\circ} \text{C}$.