Acids

Question 1

Define an acid

Answer 1

• as substance that produces hydrogen ions (H+) in aqueous soln
• hydrogen ions produced are responsible for the properties of the acids

Question 2

Properties of acids

Answer 2

1. sour taste
2. dissolve in water to form soln that conducts electricity
3. turns blue litmus paper red
4. react with reactive metals (give up electrons easily to form cations) to form hydrogen gas and salt
5. react with carbonates and hydrogen carbonates to form salt, water and CO2
6. react with metal oxides and hydroxides to form salt and water

Question 3

Property 4: Acids react with reactive metals to form hydrogen gas and salt

Answer 3

e. g. when a piece of magnesium ribbon added to dilute sulfuric acid, bubbles of hydrogen gas seen, magnesium sulfate is salt produced
- salts called sulfates when formed from sulfuric acid
- nitrates formed from nitric acid
- chlorides from hydrochloric acid

Question 4

Which metals don’t react with acids?

Answer 4

• unreactive metals, below hydrogen in reactivity series
• e.g. copper or silver, if added to dilute acids, no reaction
• lead appears to not react with dilute hydrochloric acid and sulfuric acid
• initial reaction between lead and dilute acid produces layer of lead (II) sulfate
• layer is insoluble in water, quickly forms coating arnd metal, protects metal from further attack from acid

Question 5

Property 5: react with carbonates and hydrogen carbonates to form salt, water, CO2

Answer 5

• CO2 can be tested by bubbling gas in limewater
• CO2 forms white precipitate (dont say cloudy) with limewater
• precipitate is insoluble solid particles produced in a liquid by chemical reactions

Question 6

What is the role of water in acids?

Answer 6

• acids only display properties when dissolved in water
• acids produce hydrogen ions only in water
• hydrogen ions give acids their acidic properties
• piece of magnesium ribbon into sol of hydrogen chloride in water (aqueous hcl acid), bubbles of hydrogen produced (H+ ionised by aqueous hydrogen chloride, H+ allows acid to react with magnesium)
• if added to sol of hydrogen chloride in organic solvet, no water, no reaction (H+ not ionised, no reaction with magnesium)

Question 7

Uses of acids: Sulfuric acid

Answer 7

• manufacture of fertilizers
• manufacture of detergents
• battery acid in cars

Question 8

Sulfuric acid: manufacture of fertilizers

Answer 8

-impt starting material for production of ammonium sulfate and superphosphate (active ingredients in fertilisers)

Question 9

Sulfuric acid: Manufacture of detergents

Answer 9

• converts hydrocarbons into organic acids

- organic acids then reacted with sodium hydroxide to produce the detergent

Question 10

Sulfuric acid: Battery acid in cars

Answer 10

-reacts with lead plates to lead (IV) oxide plates in battery to generate electrical energy, used to keep engine running