Acids, Bases and Alkalis Lecture Notes

Question-and-answer flashcards covering definitions, properties, examples, safety, pH scale, indicators, and reactions involving acids, bases, and alkalis.

What ion do all acids produce when dissolved in water?

Hydrogen ion (H+)

What taste is characteristic of acids?

Sour

Name the three common strong laboratory acids.

Hydrochloric acid (HCl), Sulphuric acid (H2SO4), Nitric acid (HNO3)

Which laboratory acid has the formula H2CO3?

Carbonic acid

What is the general term for bases that are soluble in water?

Alkalis

Which ion do alkalis form in aqueous solution?

Hydroxide ion (OH–)

What is produced during a neutralisation reaction between an acid and a base?

A salt and water

Give the chemical formula for sodium hydroxide.

NaOH

Which alkali is commonly found in oven cleaners?

Sodium hydroxide or caustic soda

What acid is present in vinegar?

Ethanoic acid (acetic acid)

Where is hydrochloric acid naturally found in the human body?

In the stomach

Define a concentrated acid.

An acid that contains a large amount of acid per litre of water

How does a strong acid differ from a weak acid?

A strong acid reacts rapidly with bases and other substances, while a weak acid reacts slowly.

Why should strong alkali not be used to neutralise strong acid spills on skin?

Because neutralisation releases heat and strong alkalis are also corrosive; instead, rinse with plenty of water.

What personal protective equipment is essential when handling corrosive acids or alkalis?

Eye protection and gloves

What does pH stand for?

Potenz Hydrogen—power of the hydrogen ion concentration

What pH values indicate acidic solutions?

Below pH 7

Battery acid is strongly acidic. Approximately where does it fall on the pH scale?

Around pH 0–1

What substance is considered neutral on the pH scale?

Pure water (pH 7)

Name three common laboratory indicators.

Litmus, phenolphthalein, methyl orange

What colour does blue litmus paper turn in acid?

Red

In alkali, what colour does methyl orange become?

Yellow

Which indicator is colourless in acid but pink in alkali?

Phenolphthalein

Why is universal indicator especially useful?

It shows a wide range of colours corresponding to different pH values.

How are salts named in relation to their parent acid?

By replacing the acid’s hydrogen with a metal; e.g., hydrochloric acid gives chlorides, sulphuric acid gives sulphates, nitric acid gives nitrates.

State the general word equation for an acid reacting with a base.

Acid + base/alkali → salt + water

State the general word equation for a metal reacting with an acid.

Metal + acid → salt + hydrogen

When magnesium reacts with hydrochloric acid, what gas is released?

Hydrogen gas

Which weak base is often found in indigestion tablets?

Magnesium hydroxide (milk of magnesia)

What is the colour change of bromothymol blue from acid to alkali?

Yellow in acid to blue in alkali