81. Which of the following is an example of a chemical change?

A) Melting of ice
B) Dissolving sugar in water
C) Rusting of iron
D) Boiling of water
Answer: C) Rusting of iron

82. Which of the following substances is an acid?

A) NaOH
B) HCl
C) KCl
D) NaCl
Answer: B) HCl

83. Which of the following is a basic oxide?

A) CO2
B) SO2
C) MgO
D) NO2
Answer: C) MgO

84. What is the molecular formula of benzene?

A) C6H6
B) C2H6
C) C3H6
D) C4H6
Answer: A) C6H6

85. Which of the following elements is most likely to form a cation?

A) Oxygen
B) Fluorine
C) Sodium
D) Chlorine
Answer: C) Sodium

86. Which of the following is a reducing agent?

A) Oxygen
B) Chlorine
C) Hydrogen
D) Fluorine
Answer: C) Hydrogen

87. What is the main component of natural gas?

A) Methane
B) Ethane
C) Butane
D) Propane
Answer: A) Methane

88. Which of the following is a characteristic of a metal?

A) Brittle
B) Poor conductor of electricity
C) Malleable
D) Non-magnetic
Answer: C) Malleable

89. Which of the following is an alkali metal?

A) Calcium
B) Magnesium
C) Sodium
D) Aluminum
Answer: C) Sodium

90. Which of the following is a greenhouse gas?

A) Oxygen
B) Nitrogen
C) Methane
D) Argon
Answer: C) Methane