Enthalpy of solution of NaOH (solid) in water is -41.6 kJ mol^-1. When NaOH is dissolved in water, the temperature of water :

• increases

• decreases

• does not change

• fluctuates indefinitely

222.

Hess's law is used to calculate :

• enthalpy of reaction

• entropy of reaction

• work done in reaction

• All of the above

The $∆$H°_f for CO₂ (g), CO (g) and H₂O (g) are -393.5, -110.5 and -241.8 kJ/ mol respectively. The standard enthalpy change (in kJ) for the reaction-

CO₂ (g) + H₂ (g) → CO (g) + H₂O (g) is :

• 524.1

• 41.2

• -262.5

• -41.2

If at 298 K the bond energies of C-H, C-C, C=C and H-H bonds are respectively 414, 347, 615 and 435 kJ mol^-1, the value of enthalpy change for the reaction

H₂C=CH₂ (g) + H₂ (g) → H₃C - CH₃ (g) at 298 K will be

• +250 kJ

• -250 kJ

• +125 kJ

• -125 kJ

In an isochoric process, ΔH for a system is equal to:

• p.ΔV

• pV

• E+pΔV

• ΔE

Consider the reaction,

N₂ + 3H₂ → 2NH₃

carried out at constant temperature and pressure. If $∆$H and $∆$U are the enthalpy and internal energy changes for the reaction, which of the following expression is true?

• $∆\mathrm{H} > ∆\mathrm{U}$

• $∆\mathrm{H} <∆\mathrm{U}$

• $∆\mathrm{H} = ∆\mathrm{U}$

• $∆$H = 0

The enthalpies of combustion of carbon and carbon monoxide are -393.5 and -283 kJ mol respectively. The enthalpy of formation of carbon monoxide per mole is

• 110.5 kJ

• 676.5 kJ

• -676.5 kJ

• -110.5 kJ

For the reaction

A(g) + 2B(g) → 2C (g) + 3D (g)

the change of enthalpy at 27° is 19 kcal. The value of ΔE is:

• 21.2 kcal

• 17.8 kcal

• 18.4 kcal

• 20.6 kcal

The maximum number of molecule is present in

• 15 L of H₂ gas at STP

• 5 L of N₂ gas at STP

• 0.5 g of H₂ gas

• 10 g of O₂ gas

The work done during the expansion of a gas from a volume of 4 dm³ to 6 dm³ against a constant external pressure of 3 atm, is

• -6 J

• -608 J

• +304 J

• -304 J