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.

Identify the correct statements :

A. Hydrated salts can be used as primary standard.

B. Primary standard should not undergo any reaction with air.

C. Reactions of primary standard with another substance should be instantaneous and stoichiometric.

D. Primary standard should not be soluble in water.

E. Primary standard should have low relative molar mass.

Choose the correct answer from the options given below :

$\mathrm{A}+2 \mathrm{~B} \longrightarrow \mathrm{AB}_2$

36.0 g of 'A' (Molar mass : $60 \mathrm{~g} \mathrm{~mol}^{-1}$ ) and 56.0 g of ' B ' (Molar mass : $80 \mathrm{~g} \mathrm{~mol}^{-1}$ ) are allowed to react. Which of the following statements are correct ?

A. 'A' is the limiting reagent.

B. $77.0 \mathrm{~g}$ of $\mathrm{AB}_2$ is formed.

C. Molar mass of $\mathrm{AB}_2$ is $140 \mathrm{~g} \mathrm{~mol}^{-1}$.

D. $15.0 \mathrm{~g}$ of A is left unreacted after the completion of reaction.

Choose the correct answer from the options given below :