If you had equal masses of the substances in the following pairs of compounds, which of the two would contain the greater number of ions? (a) NaBr or KCl (b) NaCl or MgCl2 (c) CrCl3 or Na2S

To determine which compound contains a greater number of ions per unit mass, we need to consider the following:

1. **Molar mass** of the compounds: Lower molar mass means more moles of substance for a given mass.
2. **Number of ions per formula unit**: This tells us how many ions are produced when the compound dissociates in water.

### (a) **NaBr or KCl**
- **NaBr**: Sodium bromide dissociates into 2 ions (Na⁺ and Br⁻).  
  Molar mass of NaBr ≈ 22.99 (Na) + 79.90 (Br) = 102.89 g/mol.
  
- **KCl**: Potassium chloride also dissociates into 2 ions (K⁺ and Cl⁻).  
  Molar mass of KCl ≈ 39.10 (K) + 35.45 (Cl) = 74.55 g/mol.

Given equal masses of both compounds, KCl has a lower molar mass, meaning for the same mass, you would have more moles of KCl, and thus more ions from KCl.

**Answer: KCl** will contain more ions.

---

### (b) **NaCl or MgCl₂**
- **NaCl**: Sodium chloride dissociates into 2 ions (Na⁺ and Cl⁻).  
  Molar mass of NaCl ≈ 22.99 (Na) + 35.45 (Cl) = 58.44 g/mol.
  
- **MgCl₂**: Magnesium chloride dissociates into 3 ions (Mg²⁺ and 2 Cl⁻).  
  Molar mass of MgCl₂ ≈ 24.31 (Mg) + 2(35.45) (Cl) = 95.21 g/mol.

Although MgCl₂ produces more ions per formula unit (3 ions compared to NaCl's 2 ions), NaCl has a significantly lower molar mass. Thus, for equal masses, you would have more moles of NaCl, and more ions from NaCl.

**Answer: NaCl** will contain more ions.

---

### (c) **CrCl₃ or Na₂S**
- **CrCl₃**: Chromium(III) chloride dissociates into 4 ions (Cr³⁺ and 3 Cl⁻).  
  Molar mass of CrCl₃ ≈ 51.99 (Cr) + 3(35.45) (Cl) = 158.35 g/mol.
  
- **Na₂S**: Sodium sulfide dissociates into 3 ions (2 Na⁺ and S²⁻).  
  Molar mass of Na₂S ≈ 2(22.99) (Na) + 32.07 (S) = 78.05 g/mol.

Na₂S has a much lower molar mass and dissociates into 3 ions, whereas CrCl₃ dissociates into 4 ions but has a much higher molar mass. For equal masses, Na₂S would result in more moles, and thus more ions.

**Answer: Na₂S** will contain more ions.

---

### Summary of Answers:
(a) **KCl**  
(b) **NaCl**  
(c) **Na₂S**

Would you like further clarification or details on these comparisons?

Here are some related questions to explore:

1. How do the lattice energies of these compounds affect their dissociation?
2. Why does the number of ions matter in determining properties like electrical conductivity?
3. How does molar mass influence the moles of a substance present in a given mass?
4. How do cation and anion sizes affect the dissociation of ionic compounds?
5. Can compounds with polyatomic ions dissociate similarly?

**Tip**: Always check the molar mass and dissociation pattern when comparing the number of ions.

Discover which compounds contain more ions when comparing equal masses of NaBr, KCl, NaCl, MgCl2, CrCl3, and Na2S. Learn the key concepts of molar mass, dissociation, and ion counts to understand which substance has a higher ion count in different compound pairs. Suitable for high school chemistry students.

Math Problem Statement

Solution

Ask a new question for Free

By Image

Math Problem Analysis

Mathematical Concepts

Formulas

Theorems

Suitable Grade Level

Related Recommendation