Extra 30 short-answer questions from Chapter:2 Acids, Bases, and Salts for Class 10 CBSE Science:
What are acids? Give two examples.
Answer:
Acids are substances that release
H⁺ ions
in aqueous solutions.
Example:
Hydrochloric acid (HCl)
,
Sulfuric acid (H₂SO₄)
What are bases? Give two examples.
Answer:
Bases are substances that release
OH⁻ ions
in aqueous solutions.
Example:
Sodium hydroxide (NaOH)
,
Calcium hydroxide (
Ca(
OH)₂)
What is an alkali? Give an example.
Answer:
An
alkali
is a
water-soluble base
.
Example:
Potassium hydroxide (KOH)
Define the pH scale.
Answer:
The
pH scale
measures the
acidity or basicity
of a solution on a scale of
0-14
.
Acidic:
pH < 7
Neutral:
pH = 7
Basic:
pH > 7
What happens to the pH of an acid when diluted?
Answer:
The
pH increases
as the concentration of
H⁺ ions
decreases
due to dilution.
What is the
colour
of litmus in acidic and basic solutions?
Answer:
Acidic solution:
Blue litmus turns red
Basic solution:
Red litmus turns blue
What is the
colour
of phenolphthalein in acids and bases?
Answer:
Acids:
Colourless
Bases:
Pink
What is the role of acids in our stomach?
Answer:
The stomach secretes
HCl
to:
Kill bacteria
Aid digestion
by breaking down food
Which acid is present in: (a) Vinegar (b) Lemon juice?
Answer:
(a)
Acetic acid (CH₃COOH)
(b)
Citric acid (C₆H₈O₇)
Which base is used in antacids? Why?
Answer:
Magnesium hydroxide (
Mg(
OH)₂)
is used in antacids to
neutralize excess stomach acid
.
What happens when an acid reacts with a metal? Give an example.
Answer:
Acids react with metals to form
salt and hydrogen gas
.
Example: Zn+2HCl→ZnCl2+H2↑Zn + 2HCl → ZnCl_2 + H_2↑Zn+2HCl→ZnCl2+H2↑
What happens when acids react with metal carbonates?
Answer:
Acids react with metal carbonates to produce
salt, water, and CO₂ gas
.
Example: Na2CO3+2HCl→2NaCl+H2O+CO2↑Na_2CO_3 + 2HCl → 2NaCl + H_2O + CO_2↑Na2CO3+2HCl→2NaCl+H2O+CO2↑
What happens when acids react with bases? Name the reaction.
Answer:
Acids react with bases to form
salt and water
. This is called a
neutralization reaction
.
Example: NaOH+HCl→NaCl+H2ONaOH + HCl → NaCl + H_2ONaOH+HCl→NaCl+H2O
What is the reaction between quicklime and water? Why is it exothermic?
Answer:
Reaction:
CaO+H2O→
Ca(
OH)2+HeatCaO + H_2O → Ca(OH)_2 + HeatCaO+H2
O→Ca
(OH)2+Heat
It is
exothermic
because heat is released.
How do metal oxides react with acids? Give an example.
Answer:
Metal oxides react with acids to form
salt and water
.
Example: CuO+2HCl→CuCl2+H2OCuO + 2HCl → CuCl_2 + H_2OCuO+2HCl→CuCl2+H2O
How do non-metal oxides react with water? Give an example.
Answer:
Non-metal oxides react with water to form
acids
.
Example: CO2+H2O→H2CO3CO_2 + H_2O → H_2CO_3CO2+H2O→H2CO3
What happens when ammonia dissolves in water?
Answer:
Reaction:
NH3+H2O→NH4OHNH_3 + H_2O → NH_4OHNH3+H2O→NH4OH
Forms
ammonium hydroxide
, a weak base.
Write the reaction of hydrochloric acid with sodium bicarbonate.
Answer:
Reaction:
NaHCO3+HCl→NaCl+CO2+H2ONaHCO_3 + HCl → NaCl + CO_2 + H_2ONaHCO3+HCl→NaCl+CO2+H2O
How is a salt formed? Give an example.
Answer:
Salts are formed by the
neutralization of acids and bases
.
Example: NaOH+HCl→NaCl+H2ONaOH + HCl → NaCl + H_2ONaOH+HCl→NaCl+H2O
Why do acids conduct electricity?
Answer:
Acids release
H⁺ ions
in water, which help in the conduction of electricity.
What is the pH of pure water? Why?
Answer:
The pH of pure water is
7
because it is
neutral
.
What is the chemical formula of baking soda? What is its use?
Answer:
Formula:
NaHCO
₃
Used in
baking
,
antacids
, and
fire extinguishers
.
What is washing soda? Write its formula.
Answer:
Washing soda is
sodium carbonate decahydrate
.
Formula:
Na₂CO
₃·10H₂O
What is Plaster of Paris? Write its formula.
Answer:
Plaster of Paris is
calcium
sulphate
hemihydrate
.
Formula:
CaSO
₄·½H₂O
What happens when an acidic solution is mixed with a basic solution?
Answer:
They undergo a
neutralization reaction
forming
salt and water
.
What is the chemical name of slaked lime? Write its formula.
Answer:
Chemical name:
Calcium hydroxide
Formula:
Ca(
OH)₂
What happens when excess CO₂ is passed through lime water?
Answer:
Lime water turns
milky
due to the formation of
CaCO
₃
.
Reaction:
Ca(
OH)2+CO2→CaCO3+H2OCa(OH)_2 + CO_2 → CaCO_3 + H_2OCa(OH)2+CO2→CaCO3+H2O
Why does tooth enamel decay in the presence of acids?
Answer:
Acids produced by bacteria in the mouth react with
calcium phosphate (tooth enamel)
, leading to decay.
What is the effect of acid rain on buildings?
Answer:
Acid rain reacts with
limestone (
CaCO
₃)
in buildings, causing damage.
Reaction:
CaCO3+H2SO4→CaSO4+CO2+H2OCaCO_3 + H_2SO_4 → CaSO_4 + CO_2 + H_2OCaCO3+H2SO4→CaSO4+CO2+H2O
How does pH affect plant growth?
Answer:
Plants grow best in
neutral/slightly acidic soil
(pH 6-7).
Too much acidity or alkalinity
damages roots and affects growth
.
