# Changing Concentration

11SCI - Chemical Tūhura

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!