A gas is allowed to expand in a well-insulated container against a constant external pressure of 2.5 atm from an initial volume of 2.50 L to a final volume of 4.50 L. The change in internal energy ΔU of the gas in joules will be

• 1136.5 J

• -500 J

• -505 J

• +505 J

A reaction having equal energies of activation for forward and reverse reactions has

• ΔS =0
• ΔG =0
• ΔH = 0
• ΔH = ΔG=ΔS = 0

Assume each reaction is carried out in an open container. For which reaction will ΔH = ΔE?

• H₂ (g) + Br₂ (g) →2HBr (g)

• C (s) + 2 H₂O (g) → 2 H₂ (g) + CO₂ (g)

• PCl₅ (g) →PCl₃ (g) + Cl₂ (g) 

• 2CO (g) + O₂ (g) → 2 CO₂ (g)

Consider the following processes Δ H (kJ/mol)

1/2 A →                               +150
3B   → 2 C + D                     -125
E + A  → 2D                        +350

For  B + D   → E + 2C, ΔH will be 

• 525 kJ/mol

• -175 kJ/mol

• -325 kJ /mol

• 325 kJ/mol

B.

-175 kJ/mol

Consider the following reactions:


Enthalpy of formation of H₂O (l) is:

• - x₂ kJ mol^-1

• + x₃ kJ mol^-1

• - x₄ kJ mol^-1

• + x₁ kJ mol^-1