Chloromethane (CH₃Cl) provides a methyl group (CH₃), and 2-chloropropane (C₃H₇Cl) provides a propyl group (C₃H₇).
These two can undergo the Wurtz reaction to couple and form 2-methylpropane (isobutane).
Thus, the correct answer is (A) chloromethane and 2-chloropropane.
The Wurtz reaction is a coupling reaction that involves two haloalkanes reacting with sodium in dry ether to form alkanes. Here, chloromethane (CH₃Cl) and 2-chloropropane (C₃H₇Cl) are the appropriate reactants for forming 2-methylpropane via the Wurtz reaction.
A block of certain mass is placed on a rough floor. The coefficients of static and kinetic friction between the block and the floor are 0.4 and 0.25 respectively. A constant horizontal force \( F = 20 \, \text{N} \) acts on it so that the velocity of the block varies with time according to the following graph. The mass of the block is nearly (Take \( g = 10 \, \text{m/s}^2 \)):