MHT-CET Chemistry · Teaching notes

Alkanes — MHT-CET Chemistry

Alkanes in MHT-CET Chemistry has no HARD question in thirty-five, and most of its MODERATE ones are the same two reactions asked in different words. Learn the series formula and the isomer counts, the Wurtz pairings, what a Grignard reagent does with any active hydrogen, and why bromine picks the tertiary H. Every PYQ is tagged.

Every subtopic, worked example, formula and trap in one printable document — answers shown, ready to share.

All 35 past questions MHT-CET Chemistry strategy MHT-CET home

Subtopic notes

Formula & revision sheet

3 formulas · 4 reference tables · 5 gotchas across all subtopics — the exam-eve cheat-sheet

The Alkane Series: Formula, Isomers, Carbon Types and Boiling Points

Formulas (1)

The Homologous Series and Its Molar Masses · Alkane molar mass $\mathrm{C_nH_{2n+2}}:\quad M = 14n + 2\ \text{g mol}^{-1}$

Reference tables (2)

Structural Isomers and Primary, Secondary, Tertiary Carbons3 rows

Isomers	Alkane	Carbon moles in n mol
2	C₄H₁₀	4nQ
3	C₅H₁₂	5nQ
5	C₆H₁₄	6nQ

Boiling Points and Uses3 rows

Question	Answer
Highest bp: 2-methoxypropane, n-butane, 2-methylbutane, n-pentane	n-PentaneQ
Highest bp among the C₆H₁₄ isomers	n-HexaneQ
Alkanes used for road surfacing	More than 35 C atomsQ

Watch out for (2)

Starting the count at ethane
→ The Homologous Series and Its Molar Masses
Neopentane as the IUPAC name
→ Structural Isomers and Primary, Secondary, Tertiary Carbons

Making Alkanes: Wurtz, Grignard Reagents and Decarboxylation

Formulas (2)

The Wurtz Reaction and Mixed Halides · Wurtz reaction $\mathrm{2R{-}X + 2Na \xrightarrow{\text{dry ether}} R{-}R + 2NaX}$
Grignard Reagents Meeting an Active Hydrogen · Grignard protonation $\mathrm{R{-}MgX + H{-}Z \rightarrow R{-}H + Mg(Z)X}\quad (Z = OH,\ OR,\ NH_2)$

Reference tables (1)

Decarboxylation and Hydrogenation of CO2 rows

Reaction	Product
Sodium propanoate + soda-lime, Δ	Ethane + Na₂CO₃ (paper keys propane)Q Decarboxylation loses a carbon, so C₂H₅COONa gives ethane. The 9 May 2023 key is propane; learn the rule, and expect the paper's answer.
CO + H₂ over Ni	Methane and waterQ

Watch out for (2)

Forgetting the self-coupled products
→ The Wurtz Reaction and Mixed Halides
Expecting an amine or an alcohol
→ Grignard Reagents Meeting an Active Hydrogen

Free-Radical Halogenation: Reactivity and Selectivity

Reference tables (1)

Halogen Reactivity and Bromine's Selectivity3 rows

Alkane + Br₂, UV	Major product	Why
2-Methylpropane (isobutane)	2-Bromo-2-methylpropane	3° HQ
(CH₃)₃CH	(CH₃)₃CBr, 99%	3° HQ
Propane	2-Bromopropane	2° HQ

Watch out for (1)

Counting hydrogens instead of ranking them
→ Halogen Reactivity and Bromine's Selectivity

PYQ weightage by concept

7 concepts · 35 PYQs — where the marks actually sit, so you know what to drill first

The Alkane Series: Formula, Isomers, Carbon Types and Boiling Points14 PYQs · 40%

Concept	PYQs	Share
Structural Isomers and Primary, Secondary, Tertiary Carbons	7	20%
The Homologous Series and Its Molar Masses	4	11%
Boiling Points and Uses	3	9%

Making Alkanes: Wurtz, Grignard Reagents and Decarboxylation17 PYQs · 49%

Concept	PYQs	Share
The Wurtz Reaction and Mixed Halides	8	23%
Grignard Reagents Meeting an Active Hydrogen	7	20%
Decarboxylation and Hydrogenation of CO	2	6%

Free-Radical Halogenation: Reactivity and Selectivity4 PYQs · 11%

Concept	PYQs	Share
Halogen Reactivity and Bromine's Selectivity	4	11%

Test yourself on Alkanes

15 past MHT-CET questions from this chapter, timed at 14 minutes and marked the way the exam marks it. You see your score and every answer the moment you finish. Free to start.

Take the Alkanes chapter test

Send them this chapter's questions. It's free for them too.