Science — CBSE Class 10 board question

(a) Electron dot structure of ethyne (C₂H₂):

Ethyne has a triple bond between the two carbon atoms.

$$\text{H} : \text{C} ::: \text{C} : \text{H}$$

(Each carbon shares 3 pairs of electrons with the other carbon and 1 pair with hydrogen.)

(b) Two differences between covalent and ionic compounds:

| Property | Covalent Compounds | Ionic Compounds |
|---|---|---|
| Melting/Boiling Point | Generally low | Generally high |
| Solubility in water | Generally insoluble or slightly soluble | Generally soluble |

(Alternatively: Ionic compounds conduct electricity in solution; covalent compounds generally do not.)

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• (a) Draw the Lewis dot structure showing a triple bond (6 shared electrons = 3 lines) between the two C atoms, with one H on each end. Examiners award marks for correct electron pairs shown as dots.
• (b) Choose any two clear, contrasting property differences. Common accepted pairs: melting/boiling points, electrical conductivity, solubility. Avoid vague statements — be specific. A table format is neat and exam-friendly for comparison questions.