Science Chapter 9: Acids and Alkalis

These flashcards cover the vocabulary and key concepts of acids and alkalis, including their properties, indicators, pH scale, neutralization reactions, and environmental impacts like acid rain.

Citric fruits

A common household source of acids, such as lemons.

Hydrochloric acid

A common laboratory acid with the chemical formula $HCl$.

Sulphuric acid

A common laboratory acid with the chemical formula $H_2SO_4$.

Nitric acid

A common laboratory acid with the chemical formula $HNO_3$.

Properties of acids

Characteristics including a sour taste, the ability to conduct electricity, and reacting with alkalis and metals.

Sodium hydroxide

A strong laboratory alkali with the formula $NaOH$ commonly found in drain cleaners.

Calcium hydroxide

An alkali also known as limewater with the chemical formula $Ca(OH)_2$.

Ammonia solution

A weak laboratory alkali with the chemical formula $NH_3$.

Properties of alkalis

Characteristics including a bitter taste, a slippery feel, the ability to conduct electricity, and reacting with acids.

Corrosive

A hazard property of acids and alkalis meaning they can burn skin and eyes.

First aid for chemical accidents

Wash the affected area under slow running water for at least $10\,\text{minutes}$ and remove contaminated clothing.

Red cabbage extract

A natural indicator containing pigments that change colour in the presence of acids or alkalis.

Litmus

An indicator used to distinguish between acidic solutions (turns blue litmus red) and alkaline solutions (turns red litmus blue).

Universal indicator

A substance that shows a range of different colours depending on the degree of acidity or alkalinity across the pH scale.

pH scale

A scale from $0$ to $14$ where a low value is more acidic, $7$ is neutral, and a high value is more alkaline.

pH meter

An instrument connected to a data-logger used to measure pH values accurately to two decimal places.

Neutralization

The chemical reaction where an acid and alkali are mixed to produce a salt and water, releasing heat in the process.

Neutralization word equation

$$\text{acid} + \text{alkali} \rightarrow \text{salt} + \text{water}$$

Antacids

Substances containing alkalis used to neutralize excess hydrochloric acid in the stomach to relieve upset.

Slaked lime

A substance added to acidic soil to regulate its pH value.

Sulphur

A substance added to alkaline soil to regulate its pH value.

Acid-metal reaction equation

$$\text{acid} + \text{metal} \rightarrow \text{salt} + \text{hydrogen}$$

Calcium carbonate

A compound found in marble and limestone with the formula $CaCO_3$ that reacts with acids.

Acid-carbonate reaction equation

$$\text{acid} + \text{carbonate} \rightarrow \text{salt} + \text{carbon dioxide} + \text{water}$$

Acid rain

Rainwater with a pH value lower than $5.6$, caused by acidic gases like sulphur dioxide and nitrogen oxide dissolving in water droplets.

Potassium hydroxide

A strong alkali with the chemical formula $KOH$.

Proper dilution procedure

Slowly add concentrated acid or alkali to a large amount of water; never add water to the concentrated substance.