Why are homologous series of carbon compounds so called? Write chemical formula of two consecutive members of a homologous series and state the part of these compounds that determines their (i) physical properties, and (ii) chemical properties.

Explanation

### Step-by-Step Solution:

1. **Definition of Homologous Series**:
- A homologous series is a group of organic compounds that have the same functional group and similar chemical properties but differ by a constant unit, typically a -CH2- group. This systematic difference in molecular structure leads to a gradual change in physical properties.

2. **Chemical Formulas of Two Consecutive Members**:
- Let's consider the homologous series of carboxylic acids.
- The chemical formula for the first member (Ethanoic acid) is **C₂H₄O₂** (or CH₃COOH).
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