Question

based on your experimental results, where did the ammonium chloride cloud form?

independent of where you placed the hydrochloric acid (hcl) and ammonia (\text{nh}_3) cotton balls.
closer to the hydrochloric acid (hcl) source.
closer to the ammonia (\text{nh}_3) source.
midway between the hydrochloric acid (hcl) and ammonia (\text{nh}_3) cotton balls.

Explanation:

Identify the reacting gases and their molar masses

Using the Grahams Law of Effusion and Gas Diffusion Experiment knowledge points
The reaction involves hydrochloric acid vapor (\(\text{HCl}\)) and ammonia gas (\(\text{NH}_3\)) diffusing from opposite ends of a tube to form solid ammonium chloride (\(\text{NH}_4\text{Cl}\)) as a white cloud:

$$ \text{NH}_3(g) + \text{HCl}(g) ightarrow \text{NH}_4\text{Cl}(s) $$

Molar masses:

$$
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$$

Compare diffusion rates using Graham's Law

Using the Grahams Law of Effusion and Gas Diffusion Experiment knowledge points
The rate of diffusion of a gas is inversely proportional to the square root of its molar mass:

$$ \frac{\text{Rate}(\text{NH}_3)}{\text{Rate}(\text{HCl})} = \sqrt{\frac{M(\text{HCl})}{M(\text{NH}_3)}} = \sqrt{\frac{36.46}{17.03}} \approx 1.46 $$

Since \(\text{NH}_3\) has a smaller molar mass, it diffuses approximately 1.46 times faster than \(\text{HCl}\).

Determine the location of the reaction product

Using the Gas Diffusion Experiment knowledge points
Because the lighter \(\text{NH}_3\) molecules travel faster and cover a greater distance in the same amount of time than the heavier \(\text{HCl}\) molecules, they meet and react at a position closer to the source of the slower-moving gas, which is the hydrochloric acid (\(\text{HCl}\)) source.

Answer:

• Independent of where you placed the hydrochloric acid (HCl) and ammonia (\(\text{NH}_3\)) cotton balls.
• Closer to the hydrochloric acid (HCl) source. (Correct answer)
• Closer to the ammonia (\(\text{NH}_3\)) source.
• Midway between the hydrochloric acid (HCl) and ammonia (\(\text{NH}_3\)) cotton balls.