Acids And Alkalis Flashcards
What is an acid?
A substance that dissociates in water to produce hydrogen ions (H⁺).
Do all compounds that contain hydrogen qualify as acids?
No, all acids contain hydrogen, but not all hydrogen-containing compounds are acids.
What are the physical properties of acids?
- Sour taste
- Turns blue litmus paper red
- pH below 7 (lower pH = stronger acid)
- Conducts electricity in aqueous state
How do acids react with metals?
Acids react with reactive metals (above hydrogen in the reactivity series) to form salt and hydrogen gas.
Which metals do not react with acids?
Unreactive metals like gold, platinum, and silver.
How can we test for hydrogen gas?
- Effervescence is observed.
- The gas is colorless and odorless.
- A lit splint produces a ‘pop’ sound near the gas.
How do acids react with metal carbonates?
They react to form salt, water, and carbon dioxide gas.
How can we test for carbon dioxide gas?
- Effervescence is observed.
- The gas is colorless and odorless.
- When bubbled through limewater, the solution turns cloudy.
What are bases?
Metal oxides and metal hydroxides.
What are alkalis?
Bases that are soluble in water, producing hydroxide ions (OH⁻).
Why is aqueous ammonia an alkali?
Because it dissociates in water to produce hydroxide ions.
What are the physical properties of alkalis?
- Bitter taste and soapy feel
- Turns red litmus paper blue
- pH above 7 (higher pH = stronger alkali)
- Conducts electricity in aqueous state
What is neutralization?
A reaction between an acid and a base/alkali to form salt and water.
How do alkalis react with ammonium salts?
On heating, alkalis react with ammonium salts to form salt, water, and ammonia gas.
Why does aqueous ammonia not react with ammonium salts?
Because no hydroxide ions are present in aqueous ammonia to react with ammonium salts.
How can we test for ammonia gas?
- Effervescence is not observed as ammonia is very soluble in water.
- The reaction mixture must be warmed to release ammonia gas.
- The gas is colorless and has a pungent smell.
- It turns moist red litmus paper blue.
What is the pH scale?
A scale from 0 to 14 that measures acidity and alkalinity.
What is the pH of pure water?
7 (neutral).
What does a pH below 7 indicate?
An acidic solution with a high concentration of hydrogen ions.
What does a pH above 7 indicate?
An alkaline solution with a high concentration of hydroxide ions.
Why is pH important in the human body?
Acidic conditions in the stomach and alkaline conditions in the intestines are necessary for digestion.
How does pH affect hair?
Hair is naturally weakly acidic. Alkaline shampoos can damage it, while mildly acidic conditioners help restore its pH.
How is pH important in food preservation?
Microorganisms do not thrive in low-pH (acidic) conditions.
Why is soil pH important for gardening?
Different plants thrive in different soil pH levels.
