Why should you care about acids, bases and salts?
Ever wondered why your soda fizzes, why soap cleans, or how table salt ends up on your fries? All of those everyday moments involve the chemistry of acids, bases and salts – the trio that keeps our kitchens, bodies and even the environment running smoothly.
💡 In Simple Words: Acids give away tiny particles called H⁺, bases give away OH⁻, and when they meet they swap partners to make a salt and water. It’s like a dance where the partners change and everyone ends up happy.
What are acids?
An acid is any substance that can donate a hydrogen ion (H⁺). Think of H⁺ as a tiny, eager messenger that loves to run off and join other things. When you squeeze a lemon, the sour juice you taste is full of H⁺ ions – that’s why it feels sharp on your tongue.
Key properties of acids
- Taste sour (like citrus or vinegar)
- Feel slippery on the skin (similar to how soap feels, but in reverse)
- Turn blue litmus paper red
- Have pH values less than 7 (the lower the number, the stronger the acid)
What are bases?
A base is a substance that can accept a hydrogen ion or give away a hydroxide ion (OH⁻). Imagine OH⁻ as a tiny stick that likes to grab H⁺ and make water. Baking soda, the powder you use in cakes, is a classic base – it feels a bit soapy and can neutralise the sting of an acid.
Key properties of bases
- Taste bitter (think of unsweetened cocoa)
- Feel slippery, like soap on your hands
- Turn red litmus paper blue
- Have pH values greater than 7 (the higher the number, the stronger the base)
What are salts?
A salt is the product you get when an acid and a base finish their little dance. The classic example is table salt – chemically called sodium chloride (NaCl). It’s formed when hydrochloric acid (HCl) meets sodium hydroxide (NaOH). The result? A neutral compound (the salt) and a splash of water.
Neutralisation reaction – the classic acid‑base dance
The general equation looks like this:
Acid + Base → Salt + Water
For instance, when HCl (acid) reacts with NaOH (base) you get NaCl (salt) and H₂O (water):
HCl + NaOH → NaCl + H₂O
Notice how the H⁺ from the acid pairs up with the OH⁻ from the base to make water. The leftovers – Na⁺ and Cl⁻ – stick together as the salt.
Worked example
Suppose you mix 25 mL of 0.1 M HCl with 25 mL of 0.1 M NaOH. Both solutions contain the same number of H⁺ and OH⁻ ions, so they completely neutralise each other. The final solution is neutral (pH ≈ 7) and contains 0.025 mol of NaCl dissolved in water.
Quick comparison – acids, bases and salts
| Property | Acids | Bases | Salts |
|---|---|---|---|
| Taste | Sour (lemon, vinegar) | Bitter (baking soda) | Generally tasteless (table salt is an exception) |
| Feel | Stinging, can burn skin | Slippery, feels soapy | Usually neutral, no special feel |
| Litmus test | Blue → Red | Red → Blue | No change (neutral) |
| pH range | 0‑7 (lower = stronger) | 7‑14 (higher = stronger) | Around 7 (neutral) |
| Common example | Hydrochloric acid (HCl) | Sodium hydroxide (NaOH) | Sodium chloride (NaCl) |
Bullet‑point recap
- Acids donate H⁺ ions; they taste sour and turn blue litmus red.
- Bases donate OH⁻ ions; they taste bitter, feel slippery and turn red litmus blue.
- When an acid meets a base, they neutralise each other, forming a salt and water.
- Neutral solutions have a pH close to 7 and show no litmus colour change.
📝 Likely Exam Questions
- Define an acid and give two everyday examples.
Answer: An acid is a substance that can donate a hydrogen ion (H⁺). Examples: lemon juice (contains citric acid) and vinegar (contains acetic acid). - Write the balanced equation for the reaction between hydrochloric acid and sodium hydroxide.
Answer: HCl + NaOH → NaCl + H₂O. - What happens to blue litmus paper when it is dipped in a basic solution? Explain why.
Answer: It turns blue to red? Actually, blue litmus stays blue in a base; red litmus turns blue. So answer: Blue litmus remains blue because bases do not provide H⁺ ions that would change its colour. - List three properties that distinguish salts from acids and bases.
Answer: (i) Salts are generally neutral (pH ≈ 7). (ii) They do not change the colour of litmus paper. (iii) They usually taste salty or are tasteless, unlike the sour or bitter taste of acids and bases. - Explain, with an example, how a neutralisation reaction is useful in everyday life.
Answer: Antacids contain bases like magnesium hydroxide that neutralise excess stomach acid (HCl), relieving heartburn. The reaction HCl + Mg(OH)₂ → MgCl₂ + 2H₂O converts the irritating acid into harmless salt and water.