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What is a base in chemistry?

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Quick answer

In chemistry, a base is a substance that accepts hydrogen ions or releases hydroxide ions (OH⁻) in water, giving it a pH above 7 and often a slippery feel. Bases are the chemical opposite of acids, and the two neutralize each other to form water and a salt.

Key things to understand

  1. A base releases hydroxide ions (OH⁻) in water, or accepts hydrogen ions from an acid.
  2. Bases have a pH above 7 — the higher the pH, the stronger the base.
  3. They often feel slippery and taste bitter (think soap or baking soda).
  4. A base and an acid neutralize each other, producing water and a salt.
  5. Strong bases (like sodium hydroxide) are highly corrosive; mild ones (like baking soda) are everyday and safe.

People also ask

What's the difference between a base and an acid?
Acids release hydrogen ions and have a pH below 7; bases release hydroxide ions (or accept hydrogen ions) and have a pH above 7. Mixed together, they neutralize each other.
Is a base the same as an alkali?
An alkali is a base that dissolves in water. All alkalis are bases, but some bases don't dissolve well, so not every base is called an alkali.
What are everyday examples of bases?
Baking soda, soap, ammonia-based cleaners, and antacids are all bases — which is why antacids relieve acidic stomach upset by neutralizing acid.