POSTLABORATORY ASSIGNMENT 1. Why is distilled water a weaker conductor than tap water? (Refer to A.1 in the Data Table.) 2. Why is solid NaCl a weak electrolyte, while aqueous NaCl is a strong electrolyte? (Refer to A.2 in the Data Table.) 3. Why is CaCO
a weak electrolyte, while CaCl
is a strong electrolyte? (Refer to A.3 and A.4 in the Data Table.) 4. Why are aqueous HC
H
O
and NH
OH weak electrolytes individually, but a strong electrolyte results when added together? (Refer to B.1 in the Data Table.) 5. Why are aqueous H
SO
and Ba(OH)
strong electrolytes individually, but a weak electrolyte results when added together? (Refer to B.2 in the Data Table
The Correct Answer and Explanation is:
1. Why is distilled water a weaker conductor than tap water?
Distilled water is a weaker conductor because it contains very few ions. It is purified to remove most dissolved minerals and impurities, so there are almost no free-moving charged particles to carry an electric current. In contrast, tap water contains dissolved salts, minerals, and other impurities that provide ions. These ions make tap water a better conductor compared to distilled water.
2. Why is solid NaCl a weak electrolyte, while aqueous NaCl is a strong electrolyte?
Solid NaCl is a weak electrolyte because the ions are locked in a rigid crystal lattice structure. In the solid state, the sodium and chloride ions cannot move freely, so electrical conductivity is very low. When NaCl dissolves in water, it dissociates completely into Na⁺ and Cl⁻ ions. These free ions move easily in solution, allowing electric current to pass, making aqueous NaCl a strong electrolyte.
3. Why is CaCO₃ a weak electrolyte, while CaCl₂ is a strong electrolyte?
CaCO₃ is a weak electrolyte because it is only slightly soluble in water. Most of the calcium carbonate remains undissolved, so only a small number of ions are present to conduct electricity. On the other hand, CaCl₂ is highly soluble in water and dissociates completely into Ca²⁺ and Cl⁻ ions. This high ion concentration makes CaCl₂ a strong electrolyte.
4. Why are aqueous HCHO and NH₄OH weak electrolytes individually, but a strong electrolyte results when added together?
Both HCHO (formaldehyde) and NH₄OH (ammonium hydroxide) are weak electrolytes because they do not ionize significantly in water. However, when combined, they react to form additional ions through a chemical reaction. The increased number of ions in solution enhances conductivity, making the mixture act as a strong electrolyte.
5. Why are aqueous H₂SO₄ and Ba(OH)₂ strong electrolytes individually, but a weak electrolyte results when added together?
H₂SO₄ and Ba(OH)₂ are strong electrolytes because they both dissociate completely in water, providing many ions. When mixed, they undergo a double displacement reaction to form BaSO₄, which precipitates out as an insoluble solid, and water. The removal of free ions from solution lowers conductivity, making the resulting mixture a weak electrolyte.
