Question

Which of the following exist as a liquid at room temperature due to the formation of associated molecules only?
A. Benzene
B. Ammonia
C. Bromine
D. Carbon disulphide

Answer 1

Hint: The question is about the phase of molecules which exist in normal condition at atmospheric temperature and pressure. One can think about their molecular structure and guess the phase of the molecule. Also, the properties of molecules contribute to its phase and analyse each molecule given in the options.

Complete step by step answer:
-The condition of room temperature is given for which the association of molecules is as normal and there will be no phase change due to the room temperature.
-Now let's analyse the options given below one by one, in the first option the benzene is an organic compound which has ${C_6}{H_6}$ as molecular formula. The benzene molecule consists of six carbon atoms in its structure which are attached in a ring which is planar with one hydrogen atom attached to each carbon atom. The benzene is composed of only carbon and hydrogen atoms that’s why it’s a hydrocarbon. The benzene is always present in the liquid phase at the room temperature condition.
- In option B the ammonia has a molecular formula $N{H_3}$ which is a gas at room temperature condition. After applying some specific conditions such as low temperature or high pressures the ammonia gas becomes a liquid and after applying more extreme conditions it becomes a solid.
-In the option C the bromine has a molecular formula $B{r_2}$ which is an oily liquid with a dark red colour. The oily liquid phase is called emulsion and not pure liquid.
- In option D the carbon disulphide has a molecular formula $C{S_2}$ which is a colourless volatile liquid. Volatile means it gets converted into a gaseous phase when exposed to air. Hence it isn’t pure liquid.
Therefore, after analysing all options the option A is the correct option.

Note: In the above question the condition of room temperature is given for which the association of molecules happens as in normal ways and there will be no phase change at the room temperature. But after applying specific conditions molecules tend to change their original phase.