Question 1: Define a giant ionic lattice and explain how the ions are arranged within it.

Answer: A giant ionic lattice is a three-dimensional structure made up of a regular pattern of positively and negatively charged ions held together by strong electrostatic forces. The ions are arranged in a repeating pattern to form a crystal structure.

Question 2: Describe the mechanism of ionic bonding that leads to the formation of a giant ionic lattice.

Answer: Ionic bonding occurs when a metal atom loses electrons to become a positively charged ion (cation), and a non-metal atom gains electrons to become a negatively charged ion (anion). These oppositely charged ions attract each other strongly, forming a regular, repeating lattice structure.

Question 1: Calculate the number of moles in 50 grams of sodium chloride (NaCl). (Molar mass of NaCl = 58.44 g/mol)

Answer: 0.855 moles

Question 2: If each unit cell of a sodium chloride lattice contains 4 Na+ ions and 4 Cl- ions, how many ions are there in 2 moles of NaCl?

Answer: 4.82 × 10^24 ions (since 1 mole contains 6.022 × 10^23 particles, so 2 moles contain 1.2044 × 10^24 units, each with 4 Na+ and 4 Cl-, total 8 ions per unit, thus 8 × 1.2044 × 10^24 = 9.6352 × 10^24 ions)

Question 1: Describe a safe procedure to test the solubility of an ionic compound in water.

Answer: Dissolve a small amount of the ionic compound in water in a clean container, stir gently, and observe whether it dissolves completely without producing any visible precipitate or excessive bubbling. Wear safety goggles and gloves during the process.

Question 2: Identify the independent and dependent variables in an experiment measuring the electrical conductivity of different ionic compounds in water.

Answer: The independent variable is the type of ionic compound, and the dependent variable is the electrical conductivity measured.

Question 1: A sample of potassium bromide (KBr) has a melting point of 734°C. Explain how the structure of KBr influences its melting point.

Answer: The strong electrostatic forces between K+ and Br- ions in the giant ionic lattice require a large amount of energy to break, resulting in a high melting point.

Question 2: In a series of ionic compounds, the melting points increase with the size of the ions. Explain why this trend occurs.

Answer: As ions become larger, the electrostatic attraction between oppositely charged ions weakens slightly, but the overall lattice becomes more stable due to increased ionic interactions. However, typically, smaller ions produce stronger attractions, so this trend indicates other factors like lattice energy are influencing melting points.

Question 1: Explain why ionic compounds tend to have high melting and boiling points.

Answer: Ionic compounds have high melting and boiling points because their giant ionic lattices are held together by strong electrostatic forces between oppositely charged ions. These forces require a significant amount of energy to break, which results in high melting and boiling temperatures.

Question 2: Describe how the structure of a giant ionic lattice affects its ability to conduct electricity in different states.

Answer: In the solid state, ionic lattices do not conduct electricity because the ions are fixed in place. When melted or dissolved in water, the ions are free to move, allowing the substance to conduct electricity. Thus, the structure determines whether the ionic compound can conduct electricity in different states.

Question 1: Discuss how the properties of sodium chloride make it useful as a preservative and seasoning.

Answer: Sodium chloride’s high solubility, ability to inhibit bacterial growth, and flavor-enhancing properties are due to its ionic lattice structure, which dissolves easily in water and releases ions that interfere with microbial processes.

Question 2: Explain how understanding ionic lattices can help in developing new materials for electronic devices.

Answer: Knowledge of ionic lattice structures aids in designing materials with specific electrical properties, such as conductance or insulation, by controlling ion types, arrangements, and lattice stability for use in semiconductors and insulators.