Question

When magnesium chloride (MgCl2) is dissolved in water, which statement must be true?(1 point)
Responses

The number of moles of the Mg2+ ions and the number of moles of the Cl– ions must each be equal to the number of moles of MgCl2.
The number of moles of the Mg 2+ ions and the number of moles of the Cl – ions must each be equal to the number of moles of MgCl 2 .

The sum of the number of moles of the Mg2+ ions and the number of moles of the Cl– ions must be equal to the number of moles of MgCl2.
The sum of the number of moles of the Mg 2+ ions and the number of moles of the Cl – ions must be equal to the number of moles of MgCl 2 .

The sum of the mass of the Mg2+ ions and the mass of the Cl– ions must be equal to the mass of MgCl2.
The sum of the mass of the Mg 2+ ions and the mass of the Cl – ions must be equal to the mass of MgCl 2 .

The mass of the Mg2+ ions and the mass of the Cl– ions must each be equal to the mass of MgCl2.

Answer 1

When magnesium chloride (MgCl₂) is dissolved in water, it dissociates into its constituent ions: one magnesium ion (Mg²⁺) and two chloride ions (Cl⁻).

Based on this dissociation, the correct statement is:

**The sum of the mass of the Mg²⁺ ions and the mass of the Cl⁻ ions must be equal to the mass of MgCl₂.**

This is true because the total mass of the products (the ions in solution) will equal the mass of the reactant (the original MgCl₂).