Acids, Bases, Indicators

Name 3 acids you can find at home.

Ethanoic Acid (in vinegar) Tartaric Acid (in grapes / cream of tartar) Citric Acid (in citrus fruits like oranges and lemons)

Sulphuric acid when dissolved in water gives ________ ions.

hydrogen

Potassium oxide when dissolved in water gives __________ ions

hydroxide

When bases dissolve in water, they release __________

hydroxide ions

pH 7 shows a _____________ solution.

neutral

Acid + Base --> ____________ + _______________

salt + water

Sodium hydroxide + sulphuric acid --->

sodium sulphate + water

Name 3 alkalis and their uses.

1. sodium hydroxide (for making soap) 2. calcium hydroxide (for neutralising excess acids in soil) 3. magnesium hydroxide (for making toothpaste)

Name 3 physical properties of alkalis.

1. Alkalis taste bitter. 2. Alkalis conduct electricity when dissolved in water. 3. Alkalis have a soapy feel. 4. Alkalis turn red litmus paper blue.

Name 3 physical properties of acids

1. All acids taste sour. 2. All acids in water have a pH of less than 7. 3. Acids turn damp blue litmus paper red. 4. Acids can conduct electricity well.

What is the pH of hydrochloric acid?

2

Can you describe a test for the effectiveness of indigestion tablets?

1. Grind the same amount of each tablet. 2. Place each tablet in a separate beaker with 100 cm3 of water 3. Dissolve thoroughly 4. To each solution, add 5 drops of an indicator (you need to specify which indicator you are using and the exact colour change you expect to see) 5. Record how much acid is added by using a burette. (Refer to Review Problems)

Describe an effect of acid rain on the environment.

1. It corrodes buildings (especially marble structures) 2. It causes water to be acidic (harming marine life). 3. It destroys forests.

Can you describe a graph that shows how the pH changes as an acid is added to an alkali?

1. The alkali to begin has a pH pf 14. 2. When the acid is added at the start, the pH changes little. 3. When the acid is neutralised, the pH drops suddenly to 7. 4. The final pH is 1. This means that excess acid has been added. (Refer to review problems)

Name 2 gases which dissolve in rain water to form acid rain.

1. carbon dioxide 2. sulphur dioxide

Acid

A substance that provides hydrogen ions when dissolved in water.

How can rust be removed?

Add small amounts of acid.

Is rust acidic or alkaline?

Alkaline

What is an indicator?

An indicator is a substance used to determine if another substance is alkaline or acidic. An indicator changes colour in the presence of an acid or alkali.

What is the colour of universal indicator when placed in water?

Green (pH 7)

Iron oxide + hydrochloric acid ---->

Iron chloride + water

The chemical name for rust is _________________.

Iron hydroxide / iron oxide

What is an alkali?

It is a base that is soluble in water. Eg. sodium oxide is soluble in water to give sodium hydroxide. Eg. potassium oxide is soluble in water to give potassium hydroxide.

Magnesium hydroxide + hydrochloric acid ---->

Magnesium chloride + water

An acid-base reaction is known as ___________

Neutralisation

Name 3 acids you can find in the lab.

Nitric acid (used to make explosives / fertilisers) Sulphuric acid (Used in car batteries) Hydrochloric acid (Used to remove rust)

What is the colour of universal indicator when dropped on a lemon?

Orange (pH 3)

Baking soda is an alkali. T / F?

True

Acids only reveal their acidic properties in water. T/F?

True.

Name an advantage of using universal indicator

Universal indicator shows whether a solution is an acid or alkali, and tells us the strength of the solution (exact pH value ---- universal indicator shows 1 colour for each pH value).