Increasing the temperature of an aqueous solution will cause:

Decrease in molarity

The correct answer is option 2. Decrease in molarity.

Increasing the temperature of an aqueous solution can cause decrease in molarity.

When the temperature of an aqueous solution increases, the volume of the solution expands due to thermal expansion. This expansion causes the solute particles to spread out over a larger volume, resulting in a decrease in the concentration of the solute.

Molarity (M) is defined as the amount of solute in moles divided by the volume of the solution in liters. As the volume increases with temperature, while the amount of solute remains constant, the molarity of the solution decreases. This is because the same number of moles of solute is distributed in a larger volume, leading to a lower concentration.

On the other hand, options (1), (3), and (4) are not necessarily affected by temperature changes:

(1) Molality (molality) is defined as the amount of solute in moles divided by the mass of the solvent in kilograms. It is independent of temperature because it is based on the amount of solute and the mass of the solvent, which are not affected by changes in temperature.

(3) Mole fraction (X) is the ratio of the number of moles of a component to the total number of moles in the solution. It is also independent of temperature since it only considers the relative amounts of the components in the solution.

(4) Percent by weight (% w/w) represents the mass of solute per 100 grams of the solution. It is not directly influenced by temperature changes, as long as the mass of the solute and the total mass of the solution remain constant.