Question
What is the formula of calcium nitride?
A. \({\text{C}}{{\text{a}}_{\text{3}}}{{\text{N}}_{\text{2}}}\)
B. \({\text{C}}{{\text{a}}_{\text{2}}}{{\text{N}}_{\text{3}}}\)
C. \({\text{Ca(N}}{{\text{O}}_{\text{2}}}{{\text{)}}_{\text{2}}}\)
D. \({\text{Ca(N}}{{\text{O}}_{\text{3}}}{{\text{)}}_{\text{2}}}\)
▶️Answer/Explanation
A
Nitride ion is N with 3- charge. Ca has +2 charge. Hence they will form \({\text{C}}{{\text{a}}_{\text{3}}}{{\text{N}}_{\text{2}}}\).
Question
Which compounds have an ionic lattice structure in the solid state?
I. Silicon dioxide
II. Sodium fluoride
III. Ammonium nitrate
A. I and II only
B. I and III only
C. II and III only
D. I, II and III
▶️Answer/Explanation
C
In the majority of silicon dioxides, the silicon atom shows tetrahedral coordination, with four oxygen atoms surrounding a central Si atom (see 3-D Unit Cell). Thus, SiO2 forms 3-dimensional network solids in which each silicon atom is covalently bonded in a tetrahedral manner to 4 oxygen atoms. Hence, silicon dioxide has covalent lattice structure.
Sodium fluoride and Ammonium nitrate have ionic lattice structures in the solid state.
Question
A solid has a melting point of 1582 °C and does not dissolve in water. It does not conduct electricity in the molten state. What type of structure does the solid have?
A. Ionic
B. Metallic
C. Giant molecular
D. Simple molecular
▶️Answer/Explanation
C
Since it does not dissolve in water and it does not conduct electricity in the molten state, it is not an ionic structure compound.
Which means it is a covalent structure compound and as it also has a high melting point, it is a giant molecular covalent compound.
Question
Which substance has the following properties?
• Low melting point
• Very soluble in water
• Does not conduct electricity when molten
A. Glucose, \({{\text{C}}_{\text{6}}}{{\text{H}}_{{\text{12}}}}{{\text{O}}_{\text{6}}}\)
B. Silicon dioxide, \({\text{Si}}{{\text{O}}_{\text{2}}}\)
C. Sodium chloride, NaCl
D. Tetrachloromethane, \({\text{CC}}{{\text{l}}_{\text{4}}}\)
▶️Answer/Explanation
A
Silicon dioxide has very high melting point. Sodium chloride conduct electricity when molten. CCl4 is not very soluble in water.
The given compound is Glucose.