Which of the following molecules is least resonance stabilized?

In the following reactions, ZnO is respectively acting as a/an :

(a) ZnO + Na₂O $$\to$$ Na₂ZnO₂

(b) ZnO + CO₂ $$\to$$ ZnCO₃

On treatment of 100 mL of 0.1 M solution of CoCl₃. 6H₂O with excess AgNO₃; 1.2 $$\times$$ 10²² ions are precipitated. The complex is :

The most abundant elements by mass in the body of a healthy human adult are: Oxygen (61.4%); Carbon (22.9%), Hydrogen (10.0%); and Nitrogen (2.6%). The weight which a 75 kg person would gain if all ¹H atoms are replaced by ²H atoms is: