A white cloud is formed when ammonia gas reacts with hydrochloric acid gas. Explain why the white cloud is formed nearer to the hydrochloric acid and discuss if doubling the amount of hydrochloric aci

a)

• (i) The student's answer is correct.
  • Size of particles (or molecular mass)
• (ii) The student's answer is correct.
  • Temperature

b) The white cloud is formed nearer to the hydrochloric acid ($\text{HCl}$) because $\text{HCl}$ gas has a higher molecular mass ($36 \text{ g/mol}$) compared to ammonia ($\text{NH}_3$) gas ($17 \text{ g/mol}$). According to Graham's Law of Diffusion, gases with lower molecular masses diffuse faster. Therefore, $\text{NH}_3$ travels a greater distance in the same amount of time, meeting the slower-diffusing $\text{HCl}$ closer to the $\text{HCl}$ source.
The student's answer is incorrect.

c) No, the location of the white cloud will not be significantly affected. The rate of diffusion of a gas is primarily determined by its molecular mass and the temperature. Doubling the amount of hydrochloric acid on the cotton wool does not change its molecular mass or the temperature of the experiment. While it might increase the intensity of the white cloud or the duration of the reaction, the relative rates at which $\text{NH}_3$ and $\text{HCl}$ diffuse, and thus the point where they meet, will remain essentially the same.
The student's answer is incorrect.