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AP Chemistry 4.4 Physical and Chemical Changes - MCQs - Exam Style Questions

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Question

A mixture of \( \text{CO}(g) \) and \( \text{O}_2(g) \) is placed in a container, as shown above. A reaction occurs, forming \( \text{CO}_2(g) \). Which of the following best represents the contents of the box after the reaction has proceeded as completely as possible?
(A)
(B)
(C)
(D)
▶️ Answer/Explanation
Detailed solution

1. Reaction Stoichiometry:
\( 2\text{CO} + \text{O}_2 \rightarrow 2\text{CO}_2 \)
The reaction consumes \( 2 \) CO molecules for every \( 1 \) O₂ molecule.

2. Analyze Initial Mixture:
From the diagram, there are more O₂ molecules than needed to react with all CO.

3. Determine Limiting Reactant:
CO is the limiting reactant; O₂ is in excess.
After reaction: Only CO₂ and leftover O₂ remain.

✅ Answer: (B)

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.

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