Which one of the following is an amphoteric oxide?

• Mn₂O₇

• CrO

• V₂O₄

• Cr₂O₃

Choose the reaction in which $∆$H is not equal to $∆$U

• C(graphite) + O₂(g) → CO₂(g)

• C₂H₄(g) + H₂(g) → C₂H₆(g)

• 2C(graphite) + H₂(g) → C₂H₂(g)

• H₂(g) + I₂(g) → 2HI(g)

The standard enthalpies of combustion of C₆H₆ (l), C_(graphite) and H₂ (g) are respectively -3270 kJ mol^-1, -394 kJ mol^-1 and -286 kJ mol^-1. What is the standard enthalpy of formation of C₆H₆ (l) in kJ mol^-1?

• -48

• +48

• -480

• +480

4.

In the reaction; A₂(g) + 3B₂(g) → 2AB₃(g), the standard entropies in (JK^-1 mol^-1) of A₂(g), B₂(g) and AB₃(g) are respectively 190, 130 and 195 and the standard enthalpy change for the reaction is -95 kJ mol^-1. The temperature (in K) at which the reaction attains equilibrium is (assuming both the standard entropy change and standard enthalpy change for this reaction are constant over a wide range of temperature)

• 500

• 400

• 300

• 200

In the following equilibrium reaction,

2A $\rightleftharpoons$ B + C

the equilibrium concentration of A, B and C are 1 × 10^-3 M, 2 × 10^-3 M and 3 × 10^-3 M respectively at 300 K. The value of K_c for this equilibrium at the same temperature is

• $\frac{1}{6}$

• 6

• $\frac{1}{36}$

• 36

Which one of the following is the correct statement?

• HCO${}_3^{-}$ is the conjugate base of CO${}_3^{2-}$

• NH${}_2^{-}$ is the conjugate acid of NH₃

• H₂SO₄ is the conjugate acid of HSO${}_4^{-}$

• NH₃ is the conjugate base of NH${}_2^{-}$

The mole fraction of methanol is in 4.5 molal aqueous solution is

• 0.250

• 0.125

• 0.100

• 0.075

0.02 mole of [Co(NH₃)₅Br]Cl₂ and 0.02 mole of [Co(NH₃)₅Cl]SO₄ are present in 200 cc of a solution X. The number of moles of the precipitates Y and Z that are formed when the solution X is treated with excess barium chloride are respectively.

• 0.02, 0.02

• 0.01, 0.02

• 0.02, 0.04

• 0.04, 0.02

The number of sigma (σ) and pi ($\mathrm{\pi }$) bonds present in 1, 3, 5, 7-octatetraene respectively are

• 14 and 3

• 17 and 4

• 16 and 5

• 15 and 4

The molecule that contains only sp² hybrid carbon atoms is

• isoprene

• acrylonitrile

• but-1-ene

• 1,3-butadiene