Q4. Find the molecular formula of chlorocyclohexane, drawn as a hexagon with Cl at one corner.
Five corners have two ring bonds each, so they are CH2; the corner with Cl has three bonds drawn, so it is CH. Hydrogens: 5 × 2 + 1 = 11. Molecular formula C6H11Cl.
Q5. Write (CH3)2CHCH2OH with its C–C, C–O and O–H bonds as dashes, and give its molecular formula.
A CH carbon bonded to two CH3 groups and to a CH2 group, which carries the OH: H3C–CH(CH3)–CH2–O–H. Molecular formula C4H10O.
Q6. Which molecular model would you use to show how much space each atom of a molecule takes up, and which to show its pattern of bonds only?
A space-filling model shows the relative size of each atom (from its van der Waals radius) and the volume it occupies. A framework model shows only the bonds, ignoring the sizes of the atoms.
Q7. Why are springs used in place of sticks for C=C bonds in some models?
A double bond is two bonds between the same two atoms. In some model kits, flexible springs fit the two connections between a pair of atom pieces more conveniently than straight sticks. This is a construction choice, not a physical model of two identical bonds. NCERT calls these ball-and-spring models, with ethene as its example. The springs look alike, so they do not show which bond is σ and which is π.
Q8. Draw (in words) the bond-line formula of pent-1-ene, CH2=CHCH2CH2CH3, and count the hydrogens it implies.
A zig-zag of five carbons with a double line between the first two. The end carbon of the double bond has 2 H, the next carbon 1 H, then two CH2 and a CH3: 2 + 1 + 2 + 2 + 3 = 10 hydrogens, C5H10.