Consider a solution that is made by dissolving 6.5 g of calcium phosphate in 375 mL of water. Is calcium phosphate an ionic compound or covalent compound? What is the chemical formula for calcium phosphate? (0.4 pts) Ionic Covalent Both Chemical Formula: When 1 molecule of calcium phosphate is added to water, what and how many ions are formed? Remember that ions are charged, so you MUST indicate the correct charge on each ion to receive credit for this question. (0.6 pts) How many moles of calcium phosphate are there in 6.5 g of calcium phosphate? (1 pt) Finally, what is the molarity of the solution? (1 pt)
The Correct Answer and Explanation is:
Answer:
- Is calcium phosphate an ionic or covalent compound?
✅ Ionic - Chemical formula:
✅ Ca₃(PO₄)₂ - When 1 formula unit of calcium phosphate dissolves in water, what and how many ions are formed?
✅ 3 Ca²⁺ ions and 2 PO₄³⁻ ions - How many moles are in 6.5 g of calcium phosphate?
Molar mass of Ca₃(PO₄)₂:
= (3 × 40.08) + (2 × (30.97 + 4 × 16.00))
= 120.24 + 2 × (30.97 + 64.00)
= 120.24 + 2 × 94.97
= 120.24 + 189.94
= 310.18 g/mol
Moles = mass / molar mass =
✅ 6.5 g / 310.18 g/mol ≈ 0.02095 mol
- What is the molarity of the solution?
Volume = 375 mL = 0.375 L
Molarity = moles / volume (L)
✅ 0.02095 mol / 0.375 L ≈ 0.05587 M
Explanation
Calcium phosphate is classified as an ionic compound because it is formed from a metal (calcium) and a polyatomic non-metal ion (phosphate). Ionic compounds typically consist of cations (positively charged ions) and anions (negatively charged ions) held together by electrostatic forces. In this case, calcium (Ca²⁺) is the cation, and phosphate (PO₄³⁻) is the anion. The chemical formula of calcium phosphate is Ca₃(PO₄)₂, which shows that three calcium ions combine with two phosphate ions to form a neutral compound.
When calcium phosphate dissolves in water, it dissociates into its constituent ions. Each formula unit of Ca₃(PO₄)₂ releases 3 Ca²⁺ ions and 2 PO₄³⁻ ions. These ions are responsible for the electrical conductivity of the solution and play key roles in chemical reactions in biological and environmental systems.
To determine the number of moles in 6.5 g of calcium phosphate, we use its molar mass, which is the sum of the atomic masses of its elements. The molar mass of Ca₃(PO₄)₂ is approximately 310.18 g/mol. Using the formula:
moles = mass / molar mass,
we get approximately 0.02095 moles of calcium phosphate in 6.5 g.
Finally, the molarity of a solution is the number of moles of solute per liter of solution. Since the solution volume is 375 mL or 0.375 L, we calculate the molarity as:
M = 0.02095 mol / 0.375 L ≈ 0.05587 M
This tells us the concentration of calcium phosphate in the solution.
