Why carbon monoxide (CO) is poisonous?

1.	It forms a complex with hemoglobin.
2.	The CO–Hb complex is about 300 times more stable than the O 2 –Hb complex.
3.	It can kill a person through suffocation on not receiving oxygen.
4.	All of the above.

An excessive content of CO₂ is responsible for global warming as:

The first ionization enthalpy decreases sharply from carbon to silicon in Group 14. What is the main reason for this decrease?

Which of the following best explains why the atomic radius of gallium is smaller than that of aluminium?

1. Poor shielding effect of the 2d-electrons

2. Poor shielding effect of the 3d-electrons

3. Poor shielding effect of the 3p-electrons

4. Poor shielding effect of the 2s-electrons

Identify the pair in which both oxides are amphoteric in nature.

1. Tl₂O₃, SiO₂

2. ${\mathrm{CO}}_2$, ${\mathrm{B}}_2{\mathrm{O}}_3$

3. ${\mathrm{B}}_2{\mathrm{O}}_3$, ${\mathrm{SiO}}_2$

4. Al₂O₃ , PbO₂

When a metal X is treated with sodium hydroxide, a white precipitate (A) is obtained, which is soluble in excess of NaOH to give soluble complex (B). Compound (A) is soluble in dilute HCl and forms compound (C). The compound (A) when heated strongly gives (D), which is used to extract the metal.

X, C & D are respectively :

Which of the following correctly describes the nature of an aqueous solution of borax?

Which of the following represents the hybridization of boron atoms in diborane, B₂H₆?

1. sp

2. s${\mathrm{p}}^2$

3. s${\mathrm{p}}^3$

4. ds${\mathrm{p}}^2$

Find the thermodynamically most stable allotrope of carbon.

Identify the statement that incorrectly describes the preparation of carbon monoxide or carbon dioxide.