Course 6.2Lesson 1 of 3
A salt is made when an acid and a base neutralise each other. Salts with the same positive or negative ion form a family. A salt of a strong acid and a strong base is neutral. One of a strong acid and a weak base is acidic, and one of a weak acid and a strong base is basic.
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Where does the salt in your kitchen come from? When hydrochloric acid and sodium hydroxide meet, the products are sodium chloride and water.
Sodium chloride is common salt. In chemistry, a salt is any ionic compound formed from an acid and a base. It has the positive ion of the base and the negative ion of the acid.
Salts that have the same positive ion or the same negative ion are a family.
It depends on the acid and the base that made the salt.
| Made from | Example | Solution is | pH |
|---|---|---|---|
| strong acid + strong base | NaCl, | neutral | about 7 |
| strong acid + weak base | , | acidic | below 7 |
| weak acid + strong base | , | basic | above 7 |
Sodium chloride is made from HCl, a strong acid, and NaOH, a strong base. Its solution is neutral. Sodium carbonate comes from the weak carbonic acid and from NaOH, and its solution is basic.
You should find that the mixture is neutral only when the two amounts are equal; any extra acid or base decides the pH.
Sea water has a lot of salt. Salt is also found as solid crystals in the ground, called rock salt. It is brown, because of impurities, and it is mined like coal. Rock salt is purified to get the salt that we eat.
This program says if a salt solution is neutral, acidic or basic, from the strength of the acid and of the base.
Try each one on your own first. If you are stuck, open a hint. Then check with Show the answer.
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