Aqueous potassium phosphate was mixed with aqueous magnesium chloride, and a crystallized magnesium phosphate product was formed. Consider the other product and its phase, and then write the balanced molecular equation for this precipitation reaction
What's the problem here? One product is given; the other is what's left over.
K3PO4(aq) + MgCl2(aq) ==> Mg3(PO4)2(s) + KCl(aq)
This is a double replacement reaction. Can you balance it from here?
What is the molecular equation for potassium phosphate mixed with magnesium chloride
K3PO4(aq) + MgCl2(aq) ==> Mg3(PO4)2(s) + KCl(aq)
To determine the balanced molecular equation for the precipitation reaction between aqueous potassium phosphate (K3PO4) and aqueous magnesium chloride (MgCl2), we need to know the solubilities of the compounds involved.
1. First, let's identify the soluble and insoluble compounds by referring to the solubility rules:
- Compounds containing Group 1 cations (e.g., K+) and ammonium (NH4+) are generally soluble.
- Compounds containing nitrate (NO3-) and acetate (C2H3O2-) anions are generally soluble.
- Compounds containing chloride (Cl-), except when paired with Ag+, Pb2+, or Hg2²+ cations, are generally soluble.
- Phosphate (PO4³-) compounds are generally insoluble, except when paired with Group 1 cations (e.g., K+), ammonium (NH4+), or when in the presence of excess acid.
2. Applying the solubility rules, we find that:
- Potassium phosphate (K3PO4) is soluble as it contains K+ and PO4³- ions.
- Magnesium chloride (MgCl2) is also soluble since it contains Mg²+ and Cl- ions.
3. Since both initial compounds are soluble, no reaction occurs directly in the solution.
4. However, upon mixing the two solutions, the ions present may combine to form an insoluble compound, known as a precipitate. In this case, magnesium phosphate (Mg3(PO4)2) is a possible precipitate as magnesium ions (Mg²+) can react with phosphate ions (PO4³-) to form an insoluble compound.
The complete balanced molecular equation for the precipitation reaction can be written as follows:
3Mg²+ (aq) + 2PO4³- (aq) → Mg3(PO4)2 (s)
This equation indicates that three magnesium ions react with two phosphate ions to produce magnesium phosphate as a solid product.
Note: The equation represents the molecular species in the reaction, and the charges are not explicitly shown. In reality, the reactants and products exist as ions in aqueous solutions.