Regents Chemistry Exam 2022
42 A sample of KCl(s) is dissolved in water to form KCl(aq). When the water in the KCl(aq) is completely evaporated, KCl(s) remains. Which statement describes a property of the KCl(s) after the water evaporated? (1) The KCl(s) becomes a molecular compound.
(2) The molar mass of the KCl(s) decreases.
(3) The melting point of the KCl(s) is unchanged.
(4) The KCl(s) conducts an electric current.
Explanation: Let's look at each statement to identify which one is true.
The KCl(s) becomes a molecular compound. A molecular compound consists of two or more nonmetals. K is a metal. We have a metal and a nonmetal making this compound ionic, not molecular. First statement is FALSE
The molar mass of the KCl(s) decreases. The molar mass of a compound does not change. Second statement is FALSE
The melting point of the KCl(s) is unchanged. TRUE
The KCl(s) conducts an electric current. FALSE Ionic compounds conduct electricity if melted or dissolved in water, not in their solid state.
Answer: 3