Explanation

 Lead tetroxide (Pb₃O₄), also known as red lead, crystallizes in the monoclinic crystal system.

Explanation

Benzene is an aromatic compound with a stable delocalized π-electron system.

It resists addition reactions (which would disrupt aromaticity) and typically undergoes substitution reactions instead.

Explanation

Knocking in an engine produces a sharp metallic sound due to premature combustion of the air-fuel mixture, which creates abnormal pressure waves.

Explanation

 Knocking causes incomplete combustion and inefficient engine performance, which reduces the efficiency of an engine.

Explanation

Glass, iron, plastic, and paper are typically considered non-recyclable domestic waste;

They are generally accepted for recycling in most communities

Explanation

 A rotary kiln used in waste treatment (like incineration or cement production) typically has four zones:

   - Drying zone

   - Preheating zone

   - Combustion zone

   - Cooling zone

Explanation

Of the elements listed, aluminum is the one that most commonly exhibits a +3 oxidation state.

Sodium typically shows a +1 oxidation state, and magnesium typically shows a +2 oxidation state.

While iron can exist in a +3 oxidation state (as in iron(III) chloride),

It also commonly exists in a +2 oxidation state (as in iron(II) sulfate), making it a transition metal with variable oxidation states. 

Explanation

 Tetraethyl lead (TEL) was historically added to gasoline to increase its octane rating and reduce knocking, but due to its environmental concerns, it has largely been phased out. 

Explanation

 Radon is a radioactive noble gas that is used in radiotherapy for cancer treatment due to its ability to emit alpha particles, which can penetrate and damage cancer cells. 

Explanation

The –SH group is present in thiols. 

A thiol is a functional group where a sulfur atom is bonded to a hydrogen atom.

The -SH group is analogous to the -OH group in alcohols, except that sulfur replaces oxygen.