DIFFUSION + SOLUBILITY

Question 1

Diffusion

Answer 1

Movement of particles in a liquid, solution or gas as they move from an area of high concentration to low concentration
They move randomly, because they are often colliding with each other (resulting in changes of direction and speed) as energy is transferred between them

Question 2

Diffusion of potassium permanganate in water

Answer 2

Method:
Place small Crystal of purple potassium permanganate in water and watch movement of pink colour as it spreads through the water. The potassium permanganate dissolves and then diffuses. Repeat at a higher temp to compare speed of diffusion

Question 3

Diffusion of hydrogen chloride and ammonia gases

Answer 3

Method:
Soak a piece of cotton wool in concentrated hydrochloric acid and add another piece in concentrated ammonia solution. Place the pieces of cotton wool at either end of a tube and watch where the product forms.

Question 4

Core practical 1
Investigate the solubility of a solid in water
Method

Answer 4

Method:

1. Pour approx 50cm cubed of tap water into a beaker
2. Add the solute one spatula at a time , with stirring until no more solute dissolves and some solid remains und is solved in the beaker
3. record mass of empty evaporation basin
4. Filter the mixture of solution and und is solved crystals into the evaporating basin
5. record mass of evaporating basin with solution
6. evaporate the water from the solution until you have dry crystals (Bunsen burner)
7. Record mass of evaporating basin containing dry crystals

Question 5

Solubility equation

Answer 5

Solubility (per 100g of water)

= (mass of solute (g) Divided by mass of solvent (g)) Then multiply all of that by 100

Question 6

If an evaporating basin is heated too strongly, some of the solute spits out of the boiling solution and small crystals form on the surrounding bench. Explain how this error would affect the calculated value for the solubility of potassium chloride.

Answer 6

• less solute left behind
• would like like you had more solvent
• would unfairly lower the solubility of potassium chloride

Question 7

Conclusion for potassium permanganate in water

Answer 7

Conclusion:

Diffusion is random movement and happens quicker at higher temps, when particles have more kinetic energy

Question 8

Diffusion of hydrogen chloride and ammonia gases results

Answer 8

Hydrogen chloride gas reacts with ammonia gas to produce white solid ammonium chloride, according to the equation: hydrogen chloride + ammonia -> ammonium chloride
A ring of white solid is seen nearer the hydrogen chloride end of the tube
Conclusion: lighter particles like ammonia diffuse faster than particles like hydrogen chloride.
HCL (g) + NH3 (g) -> NH4Cl (s)