Changing Concentration

11SCI - Chemical TÅ«hura

Finn LeSueur

2020

Concentration: Collision Theory

  • Concentration is easily thought of like raro - the more raro particles you add to your drink, the stronger it is!
  • The more particles there are, the higher the chance there is of particles bumping into each other
  • The more bumps there are, the greater number of successful collisions overall
  • It does not increase the probability of successful collisions

Dilutions

  • To change the concentration we must dilute one of our reactants.
  • Question: What do we dilute raro with (we use the same in chemistry)?
  • Answer: Water! \(H_{2}O\)

Dilutions Explained

  • In Year 11 we will do dilutions in percentages. For example, 90% \(HCl\), 80% \(HCl\) or 30% \(HCl\)
  • For \(10ml\) of 80% \(HCl\) this means 80% of the \(10ml\) is \(HCl\) and 20% is water!
  • Calculate the \(ml\) of acid and water for the above solution ^

\[\text{Volume of Acid} = \frac{percentage}{100} \times \text{total volume}\]

Task: Calculate the \(HCl\) and \(H_{2}O\) for each solution

\[\text{Volume of Acid} = \frac{percentage}{100} \times \text{total volume}\]

Concentration Volume \(ml\) of \(HCl\) \(ml\) of \(H_{2}O\)
90% 100ml
80% 75ml
75% 50ml
50% 50ml
30% 50ml
Concentration Volume \(ml\) of \(HCl\) \(ml\) of \(H_{2}O\)
90% 100ml \(90ml\) \(10ml\)
80% 75ml
75% 50ml
50% 50ml
30% 50ml
Concentration Volume \(ml\) of \(HCl\) \(ml\) of \(H_{2}O\)
90% 100ml \(90ml\) \(10ml\)
80% 75ml \(60ml\) \(15ml\)
75% 50ml
50% 50ml
30% 50ml
Concentration Volume \(ml\) of \(HCl\) \(ml\) of \(H_{2}O\)
90% 100ml \(90ml\) \(10ml\)
80% 75ml \(60ml\) \(15ml\)
75% 50ml \(37.5ml\) \(12.5ml\)
50% 50ml
30% 50ml
Concentration Volume \(ml\) of \(HCl\) \(ml\) of \(H_{2}O\)
90% 100ml \(90ml\) \(10ml\)
80% 75ml \(60ml\) \(15ml\)
75% 50ml \(37.5ml\) \(12.5ml\)
50% 50ml \(25ml\) \(25ml\)
30% 50ml
Concentration Volume \(ml\) of \(HCl\) \(ml\) of \(H_{2}O\)
90% 100ml \(90ml\) \(10ml\)
80% 75ml \(60ml\) \(15ml\)
75% 50ml \(37.5ml\) \(12.5ml\)
50% 50ml \(25ml\) \(25ml\)
30% 50ml \(15ml\) \(35ml\)

Diagrams

Drawing a diagram is a very good way to visually show the amount of water and acid/base in your dilutions. Perhaps this could go in your method!