Question
A student combines a solution of \(NaCl\)(aq) with a solution of \(AgNO_3\)(aq) , and a precipitate forms. Which of the following is evidence that ionic bonds formed during the precipitation?
A The resulting solution is colorless.
B The resulting solution conducts electricity.
C The precipitate has a high melting point.
D The temperature of the solution did not change significantly during the precipitation.
▶️Answer/Explanation
Ans:C
A characteristic of compounds containing ionic bonding is a high melting point.
Question
A beaker was half filled with freshly distilled \(H_2O\) and placed on a hot plate. As the temperature of the water reached 100°C , vigorous bubbling was observed in the beaker. The gaseous contents of the bubbles were analyzed. The presence of which of the following substances would support the claim that the observed phenomenon was a physical change?
A \(H_2(g)\)
B \(O_2(g)\)
C \(CO_2(g)\)
D \(H_2O(g)\)
▶️Answer/Explanation
Ans: D
When water boils, a physical change takes place in which \(H_2O(l)\) changes to \(H_2O(g)\). If the bubbles formed were \(H_2O(g)\), then the phenomenon would be a physical change.
Question
When students added 2.0g of NaI crystals to 100.mL of \(Pb(NO_3)_2(aq)\) , a yellow precipitate formed. After the solution was filtered, the yellow solid was dried and weighed. Data from the experiment are shown in the table above. Which of the following claims is best supported by the observations?
A A physical change occurred when a new yellow compound was formed.
B A physical change occurred when the color of the NaI solid added changed to yellow when mixed with water.
C A chemical change occurred when a yellow, insoluble compound with a larger mass than the original NaI formed.
D A chemical change occurred when covalent bonds between the yellow solid and water were broken during drying.
▶️Answer/Explanation
Ans:C
A chemical change occurred because of the formation of a new yellow, insoluble compound with a larger mass than that of NaI.
Refer to the following.
\( M^{+}\) is an unknown metal cation with a +1 charge. A student dissolves the chloride of the unknown metal, MCI, in enough water to make 100.0 mL of solution. The student then mixes the solution with excess \(AgN0_3\) solution, causing AgCl to precipitate. The student collects the precipitate by filtration, dries it, and records the data shown below. (The molar mass of AgCl is 143 g/mol.)
Mass of unknown chloride, MCI 0.74 g
Mass of filter paper 0.80 g
Mass of filter paper plus AgCl precipitate 2.23 g
Question
Which of the following diagrams best represents the \(AgNO_{3}\) solution before the reaction occurs? Note: water molecules are represented by the symbol
▶️Answer/Explanation
Ans:A
Refer to the following.
\( M^{+}\) is an unknown metal cation with a +1 charge. A student dissolves the chloride of the unknown metal, MCI, in enough water to make 100.0 mL of solution. The student then mixes the solution with excess \(AgN0_3\) solution, causing AgCl to precipitate. The student collects the precipitate by filtration, dries it, and records the data shown below. (The molar mass of AgCl is 143 g/mol.)
Mass of unknown chloride, MCI 0.74 g
Mass of filter paper 0.80 g
Mass of filter paper plus AgCl precipitate 2.23 g
Question
Which of the following diagrams best represents the \(AgNO_{3}\) solution before the reaction occurs? Note: water molecules are represented by the symbol
▶️Answer/Explanation
Ans:A