When testing the effect of molecular weight on diffusion, the hydrochloric acid and ammonia molecules were placed at different ends of a sealed tube. The ammonium chloride that formed when the molecules diffused towards each other and met was closer to the ammonia end of the tube.

a. True

b. False

When testing the effect of molecular weight on diffusion using hydrochloric acid and ammonia molecules at different ends of a sealed tube, the ammonium chloride formed when the molecules diffused towards each other and met would be closer to the hydrochloric acid end of the tube. The correct answer is, therefore, false.

According to Graham's law, the rate of diffusion of molecules is inversely proportional to the square root of the molar mass of the molecule. Thus, there is an inverse relationship between diffusion rate and the molar mass of molecules at a particular temperature.

The molecular weight of hydrochloric acid is approximately 36.5 g/mol. while that of ammonia is approximately 17.0 g/mol. Hence, at equal temperature, ammonia molecules would diffuse faster than hydrochloric acid molecules.

In the sealed tube, ammonia molecules would diffuse faster than hydrochloric acid molecules and, hence, meet the hydrochloric acid molecules closer closer to the hydrochloric acid end of the tube.

Therefore, the ammonium chloride that would be formed would be closer to the hydrochloric acid end of the tube rather than the ammonia end of the tube.

More on the rate of diffusion can be found here:  

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