Diffusion Flashcards
What is diffusion?
The spreading out of particles in a gas or liquid from an area of high to lower concentration until evenly spread.
Diffusion cannot happen in a solid; it must dissolve before diffusing.
What factors affect diffusion?
Temperature and the molecular weight (Mr) of the compound.
As temperature increases, the diffusion rate increases; as molecular weight increases, the diffusion rate decreases.
What happens in the white ring experiment?
Vapours from soaked cotton diffuse and move towards the center of the tube, forming a white ring of ammonium chloride (NH4Cl) nearer to the HCl cotton.
NH3 (Mr = 17) moves faster than HCl (Mr = 36.5) due to its lower molecular weight.
What type of reaction occurs between HCl and NH3 in the white ring experiment?
Neutralization reaction.
This reaction can be reversed by heating ammonium chloride.
What occurs during the thermal decomposition of ammonium chloride?
Ammonium chloride is thermally decomposed, releasing a mixture of hydrogen chloride and ammonia gas.
The chemicals react again to form ammonium chloride at the exit of the test tube.
What is the mixture of gases in the center of the test tube during the experiment?
Hydrogen chloride and ammonia.
These gases react to form ammonium chloride.
Why does the experiment take a few minutes despite gases traveling rapidly?
Because gases do not travel in straight lines and collide with particles already in the test tube.
What is the chemical name for HCl when in liquid form?
Hydrochloric acid.
In gas form, it is referred to as hydrogen chloride.
