If Avogadro number N_A, changed from 6.022 x 10²³ mol^-1 this would change

• the definition of mass in units of grams

• the mass of one mole of carbon

• the ratio of chemical species to each other in the balanced equation

• the ratio of chemical species to each other in the balanced equation

The formation of the oxide ion O^2- (g), from oxygen atom requires first an exothermic and then an endothermic step as shown below,


Thus, the process of formation of O^2- in the gas phase is unfavourable even though O^2- is isoelectronic with neon. It is due to the fact that

• electron repulsion outweighs the stability gained by achieving a noble gas configuration

• O^- ion has comparatively smaller size that oxygen atom

• oxygen is more electronegative

• oxygen is more electronegative

Decreasing order of stability of  is

What is the pH of the resulting solution when equal volumes of 0.1 M NaOH and 0.01 M HCl are mixed?

• 12.65

• 2.0

• 7.0

• 7.0

5.

20.0 g of a magnesium carbonate sample decomposes on heating to give carbon dioxide and 8.0 g magnesium oxide. What will be the percentage purity of magnesium carbonate in the sample? (Atomic weight of Mg =24)

• 75

• 96

• 60

• 60

What is the mass of precipitate formed when 50 mL of 16.9% solution of AgNO₃ is mixed with 50 mL of 5.8% NaCl solution?

(Ag = 107.8, N = 14, O = 16, Na = 23, Cl = 35.5)

• 28 g

• 3.5 g 

• 7 g 

• 7 g 

Which is the correct order of increasing energy of the listed orbitals in the atom of titanium?

• 3s 4s 3p 3d

• 4s 3s 3p 3d

• 3s 3p 3d 4s

• 3s 3p 3d 4s

A gas such as carbon monoxide would be most likely to obey the ideal gas law at

• high temperatures and low pressures

• low temperatures and high pressures

• high temperatures and high pressures

• high temperatures and high pressures

The heat of combustion of carbon to CO₂ is -395.5 kJ/mol. The heat released upon the formation of 35.2 g CO₂ from carbon and oxygen gas is 

• -315 kJ

• +315 kJ

• -630 kJ

• -630 kJ

Which one of the following pairs of the solution is not an acidic buffer?

• HClO₄ and NaClO₄

• CH₃COOH and CH₃COONa

• H₂CO₃ and Na₂PO₄

• H₂CO₃ and Na₂PO₄