Complete the following sentences by choosing the correct option from the brackets:
(a) The oxide that dissolves in caustic potash (KOH) is ............... . [ZnO / CuO]
(b) The reaction that takes place at the anode during the electrolysis of molten lead bromide is ............... . [2Br - 2e– ⟶ 2Br– / 2Br– - 2e– ⟶ Br2]
(c) The volume occupied by 8 grams of oxygen gas at STP is ............... litres. [5.6 / 8.96] [Atomic weight of O = 16]
(d) ............... does not give hydrogen gas when it reacts with cold and very dilute nitric acid. [Cu / Mn]
(e) ............... is a polar covalent compound. [HCl / CCl4]
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(a) The oxide that dissolves in caustic potash (KOH) is ZnO.
Reason — ZnO is amphoteric in nature, so it dissolves in both acids and alkalis like KOH.
ZnO + 2KOH ⟶ K2ZnO2 + H2O
(b) The reaction that takes place at the anode during the electrolysis of molten lead bromide is 2Br- - 2e- ⟶ Br2.
(c) The volume occupied by 8 grams of oxygen gas at STP is 5.6 litres.
Reason —
Molar mass of O2 = 32 g
32 g of O2 at STP occupies 22.4 L
∴ 8 g of O2 occupies $\frac{22.4}{32}$ × 8 = 5.6 L
(d) Cu does not give hydrogen gas when it reacts with cold and very dilute nitric acid.
Reason — Copper lies below hydrogen in the activity series, so it does not liberate hydrogen with nitric acid.
(e) HCl is a polar covalent compound.
Reason — HCl is formed by sharing of electrons between H and Cl, but due to large electronegativity difference, the bonding electrons are unequally shared, giving the molecule a polar character. CCl4 is a non-polar covalent compound due to symmetric structure.