Magnesium chloride (MgCl2) is readily soluble in which of the following solvents?

Introduction / Context:
Solubility of salts depends on the nature of both the solute and the solvent. Ionic compounds such as magnesium chloride dissociate into ions when dissolved in suitable polar solvents. Recognising which solvent will dissolve such a salt is an important part of understanding solutions in chemistry. This question asks you to identify the medium in which MgCl2 is soluble among several common liquids.

Given Data / Assumptions:

• The solute is magnesium chloride, an ionic compound with formula MgCl2.
• Options include petrol, acetone, kerosene, water, and liquid nitrogen.
• We assume typical room temperature conditions.
• We use the principle that polar solvents dissolve ionic and polar solutes, while nonpolar solvents dissolve nonpolar solutes.

Concept / Approach:
Magnesium chloride consists of Mg^2 plus and Cl minus ions held together by ionic bonds. Water is a highly polar solvent with a high dielectric constant and is very effective at solvating ions, so ionic salts like MgCl2 are usually soluble in water. Petrol and kerosene are mixtures of nonpolar hydrocarbons and do not dissolve ionic salts well. Acetone is a polar organic solvent but is less effective at dissolving many simple inorganic salts than water. Liquid nitrogen is a cryogenic nonpolar fluid and is not a practical solvent for such salts. Therefore, water is the correct solvent for dissolving magnesium chloride under ordinary conditions.

Step-by-Step Solution:
Step 1: Recognise that MgCl2 is ionic and will dissociate into Mg^2 plus and Cl minus ions in a polar solvent. Step 2: Water molecules are polar, with partial positive charge on hydrogen and partial negative charge on oxygen, and can surround ions effectively. Step 3: The strong interaction between water molecules and ions allows water to pull Mg^2 plus and Cl minus away from the crystal lattice and keep them in solution. Step 4: Petrol and kerosene are nonpolar hydrocarbon liquids; they interact weakly with ions and cannot break ionic bonds effectively. Step 5: Acetone is somewhat polar but is not typically used to dissolve simple inorganic salts like magnesium chloride because water performs this task much better. Step 6: Liquid nitrogen is extremely cold and nonpolar, used mainly as a refrigerant, not as a solvent for ionic compounds. Hence, water is the correct choice.

Verification / Alternative check:
In laboratory practice, magnesium chloride is usually supplied as a white crystalline solid that dissolves easily in water to form clear solutions. Solubility tables list MgCl2 as highly soluble in water. When students attempt to dissolve table salt or other ionic salts in petrol or kerosene, they observe that the solid remains undissolved, illustrating the principle that like dissolves like. Acetone is more commonly used to dissolve organic compounds, further confirming that water is the natural solvent for MgCl2 in basic chemistry contexts.

Why Other Options Are Wrong:
Petrol: A mixture of nonpolar hydrocarbons; it does not dissolve ionic salts like magnesium chloride.
Acetone: Polar organic solvent, but not the standard or most effective solvent for inorganic salts such as MgCl2 in simple experiments.
Kerosene: Another nonpolar hydrocarbon liquid, unsuitable for dissolving ionic compounds.
Liquid nitrogen: Used for cooling and cryogenics; it is nonpolar and extremely cold, not used as a solvent for routine salt dissolution.

Common Pitfalls:
A common mistake is to assume that any liquid might dissolve any solid. Another error is to choose acetone simply because it is sometimes used as a laboratory solvent. To avoid these problems, remember the guiding rule that ionic and polar compounds dissolve best in polar solvents like water. This rule immediately points to water as the solvent that will readily dissolve magnesium chloride.

Final Answer:
Magnesium chloride is readily soluble in water.