Identify the correct statements : A. The molality of 2.5 g of...

Statement A : Molality is given by the number of moles of solute divided by the mass of solvent in kg.
Moles of ethanoic acid $= \dfrac{2.5}{60} = \dfrac{1}{24}$ mol
Mass of benzene $= 75$ g $= 0.075$ kg
Molality $= \dfrac{1/24}{0.075} = \dfrac{1000}{24 \times 75} = \dfrac{1000}{1800} = \dfrac{5}{9} = 0.556$ m
Statement A is correct.

Statement B : Molarity is given by the number of moles of solute divided by the volume of solution in litres.
Moles of NaOH $= \dfrac{5}{40} = \dfrac{1}{8}$ mol
Volume of solution $= 450$ mL $= 0.45$ L
Molarity $= \dfrac{1/8}{0.45} = \dfrac{1000}{8 \times 450} = \dfrac{1000}{3600} = \dfrac{5}{18} = 0.278$ M
Statement B is correct.

Statement C : The solubility of gases (like oxygen) in water increases with a decrease in temperature. Therefore, cold water contains more dissolved oxygen, making aquatic species more comfortable.
Statement C is correct.

Statement D : According to Henry's law, the solubility of a gas in a liquid is directly proportional to the pressure of the gas. Thus, solubility decreases with a decrease in pressure.
Statement D is incorrect.

Statement E : The mole fraction of component B is the ratio of the number of moles of B to the total number of moles in the mixture.
$x_B = \dfrac{n_B}{n_A + n_B}$
Statement E is incorrect.

Therefore, only statements A, B, and C are correct.

Answer: A, B and C only