Which allotrope of carbon is used in pencils? MCQ with Answer and Explanation

Explanation:
Natural gas is primarily methane (CH₄), typically 70-90%, along with small amounts of ethane, propane, butane, and other hydrocarbons. It is a fossil fuel formed from the remains of ancient marine organisms. CNG (compressed natural gas) is methane stored at high pressure. LPG (liquefied petroleum gas) mainly contains propane and butane. Methane has the highest calorific value among the given options per unit mass.

Explanation:
Oleum, also known as fuming sulfuric acid, is a solution of sulfur trioxide (SO3) in concentrated sulfuric acid (H2SO4). Its chemical formula is often represented as H2S2O7 (disulfuric acid or pyrosulfuric acid), which is essentially H2SO4 + SO3. It is an intermediate in the Contact process.

Explanation:
The modern periodic law states that properties of elements are periodic functions of their atomic numbers (number of protons). This was established by Henry Moseley. Mendeleev's original table used atomic mass, but the modern table resolves anomalies by ordering by atomic number.