# Acids, bases and salts

> What makes copper (II) sulphate a salt?


## Objectives

- Define an acid, a base and an alkali, and name common examples.
- State that an acid and a base react to give a salt and water.
- Name a salt from its metal and its acid: chloride, sulphate, nitrate.

## 1. Acids, bases and salts: from zero




## 2. Not all salts are for food

Predict: what do NaCl and $CuSO_4$ have in common?

- Both taste salty
- Each has a metal joined to the rest of an acid ✓
- Both dissolve in water

In both, a metal has taken the place of the hydrogen of an acid: Na with the Cl of hydrochloric acid, Cu with the $SO_4$ of sulphuric acid. That is what makes them salts, not their taste or dissolving.

[ar-EG] في الاتنين فيه metal واخد مكان الـ hydrogen بتاع acid: الـ Na مع الـ Cl بتاع الـ hydrochloric acid، والـ Cu مع الـ $SO_4$ بتاع الـ sulphuric acid. وده اللي بيخليهم salts، مش الطعم ولا الذوبان.
## 3. Acids

Acid A substance that gives positive hydrogen ions ($H^+$) when dissolved in water. An **ion** is an atom, or a group of atoms, with an electric charge. You'll study ions later in Chapter 1. Common acids Acids taste sour and turn litmus red. Never taste them in the lab!


## 4. Bases

Base A substance that reacts with an acid to give a salt and water. Many metal oxides and metal hydroxides are bases. Examples: copper (II) oxide, CuO, and magnesium hydroxide, $Mg(OH)_2$. Two bases You'll meet metal oxides as bases again in the next lesson.


## 5. Alkalis

Alkali A base that dissolves in water, giving hydroxide ions ($OH^-$). Examples: sodium hydroxide, NaOH, and ammonium hydroxide, $NH_4OH$. Alkalis turn litmus blue. NaOH is an acid, because its formula contains H.


## 6. Acid + base → salt + water

An alkali and an acid give a salt and water Salt A compound formed when the hydrogen of an acid is replaced by a metal (or ammonium). Naming rule: the metal's name from the base + the ending from the acid. Copper (II) oxide + sulphuric acid → copper (II) sulphate + water.


## 7. Name the parent acid

Which pair reacts to give zinc nitrate and water?

- ZnO and $H_2SO_4$
- ZnO and $HNO_3$ ✓
- ZnO and HCl
- NaOH and $HNO_3$

Zinc nitrate takes its metal, zinc, from the base ZnO, and its ending, nitrate, from nitric acid, $HNO_3$. A base and an acid give a salt and water.

[ar-EG] الـ zinc nitrate بياخد الـ metal بتاعه، الـ zinc، من الـ base اللي هو ZnO، ونهاية اسمه، nitrate، من الـ nitric acid، $HNO_3$. والـ base مع الـ acid بيدّوا salt و water.
## 8. Summary

Acids give hydrogen ions, $H^+$, in water: HCl, $H_2SO_4$, $HNO_3$. Bases react with acids to give a salt and water. Many metal oxides and hydroxides are bases. Alkalis are bases that dissolve in water, giving $OH^-$: NaOH, $NH_4OH$. Chlorides, sulphates and nitrates come from HCl, $H_2SO_4$ and $HNO_3$. Back to the hook: NaCl and $CuSO_4$ are both salts. In each, a metal replaced the hydrogen of an acid. Key words: **acid**, **base**, **alkali**, **salt and water**, **chloride**, **sulphate**, **nitrate**. Can you explain why $CuSO_4$ is a salt of sulphuric acid? In $CuSO_4$, copper has replaced the hydrogen of sulphuric acid, $H_2SO_4$. The $SO_4$ group comes from the acid, so the salt is a sulphate.



Chapter: Transition Elements (https://yaani.ai/ar/learn/chemistry/chem-s3-en.ch1)
Source: https://yaani.ai/ar/lesson/chem-s3-en.lesson-chem.acids-bases-salts