Number of moles and number of molecules in 1.4187 L of $\mathrm{SO}_2$ at STP respectively are

The ratio of mass percentage (w/w) of C : H in a hydrocarbon is 12 : 1. It has two carbon atoms. The weight (in g) of CO₂(g) formed when 3.38 g of this hydrocarbon is completely burnt in oxygen is :

(Given : Molar mass in g mol^–1 C : 12, H : 1, O : 16)

The mass of iron converted into Fe₃O₄ by the action of 18 g of steam is:

(Given: Molar mass of H, O and Fe are 1, 16 and 56 g mol⁻¹ respectively)

Assume iron is present in excess:

For the given reaction;

CaCO₃ + 2HCl → CaCl₂ + H₂O + CO₂

If 90 g CaCO₃ is added to 300 mL of HCl which contains 38.55% HCl by mass and has density 1.13 g mL⁻¹, then which of the following option is correct?

Given molar mass of H, Cl, Ca and O are 1, 35.5, 40 and 16 g mol⁻¹ respectively.