Acids & Alkalis In Everyday Life

1. Acids & Alkalis In Everyday Life

2. Today’s Lesson • Some recapping from last lesson • Acids & Alkalis in everyday life • Corrosion • Start Design Task

3. Basics • Acid + Metal Hydroxide  Metal Salt + Water • Acid + Metal  Metal Salt + Hydrogen • Acid + Metal Carbonate  Metal Salt + Water + Carbon Dioxide • Acid + Metal Oxide  Metal Salt + Water

4. Neutralization • What makes something an acid?? • For Hydrochloric Acid: • HCl (aq)  H+ (aq) + Cl- (aq) • What makes a base a base? • For Sodium Hydroxide: • NaOH (aq)  Na+ (aq) + OH- (aq)

5. Neutralization Reaction • Below is an example of a neutralization reaction: • HCl (aq) + NaOH (aq) NaCl (aq) + H2O (l) • As ions, you would write it like this: • H+ (aq) + OH- (aq)  H2O (l) • Note how the Hydrogen and Hydroxide form water!

6. Let’s Get Neutral • Acids and bases are commonly used as cleaning products. • There are also different ways in neutralize different problems: • Insect stings: these are acidic so adding a weak alkali (like baking soda or calamine lotion can get rid of the sting • Indigestion: Your stomach has acid in it – so if your stomach gets unsettled acid can go up your esophagus. Adding baking soda can get rid of the problem

7. Continued • Soil treatment. Different plants like to grow at different pH levels. If the soil is acidic, you can add a alkali such as lime (not the fruit). If it’s alkali, you can add a weak base. • Factory Waste. Factory waste often contains acid. Slacked lime can be used to neutralize the acid to make salt and water. What other problems can this cause??

8. Acid Rain • Adding certain compounds in the air can cause acid rain. Below are some examples: • Carbon Dioxide can make carbonic acid • Sulfur dioxide can make Sulfuric Acid • Nitric Oxides can make Nitric oxide • Many older buildings are made of limestone, which can become corroded from acid rain.

9. Corrosion • When a metal is attacked by air, water, or other substances in its surroundings, the metal is said to corrode. • Some examples include: • Iron rusting in air forming Iron Oxide • Sodium metal reaction with water to form Sodium Hydroxide • Lead rusting in air forming Lead Oxide

10. Prevention Corrosion • Below are some ways to minimize corrosion: • Painting – Painting prevents air and water coming into direct contact with the metal. • Grease – Tools and machine parts can be coated with grease or oil to stop them coming into contact with water or air. • Plastic – Steel and other metals can be covered with plastic (powder coated) and stops weathering of the metal.

11. Preventing Corrosion • Galvanizing – Iron can be covered with Zinc which is less reactive than Iron. Zinc is more expensive than Iron – but a thin covering of it can protect the Iron from air and water. • Tin Plating – Steel cans are covered with Tin to stop the can from rusting from air or water. • Chromium Plating – Chromium is often used as a coating for car parts to make sure the iron is protected from the elements. It’s also very shiny so it is astatically pleasing

12. Preventing Corrosion • Sacrificial Protection – Zinc and Magnesium are more reactive than Iron. As such, they will oxidize before Iron. As such, Iron will not corrode until there is no Zinc or Magnesium left in elemental form. • Examples of where this occurs is Zinc bolts on large ships. The Zinc bolts will oxidize but the ship will not corrode unless all of the Zinc has all oxidized.

13. Doe’s Aluminium Corrode • Unlike Iron Oxide, Aluminium Oxide is quite strong and acts as a protective layer for the metal. • As such, the Aluminium Oxide is needed to protect the rest of the aluminium in elemental form. It also stops air and water getting into the Aluminium.

14. Questions • Read page 50/51 and answer Q1-6 in your book. • Read page 88/89 and answer Q 1-6. • We will also start our next design task which is on corrosion. • The write-up needs to be finished by next week so I can get the equipment ready by next term.