Chemical Thermodynamics

Which of the following is an exothermic reaction?

• melting ice

• dissolving sugar

• oxidation of iron

Which of the following is an exothermic reaction?

• condensation

• melting ice

• dissolving sugar in water

Two objects (A and B) of the same temperature are in contact with each other. Which of the following statements is true?

• Heat transfers from object B to object A, because molecules from B collide with those from A

• Although the molecules collide, no heat transfers because there is no temperature difference between the objects.

• No heat transfers, because there are no collisions between the molecules of the objects.

 $\ The\ reaction\ 2NO(g)-->N2(g)+O2(g)\ has\ a\ \Delta H\ =\ -180.5\ kJ$  . How much heat will be required to produce 44.8 L of NO  by the reverse reaction?

• 180.5 kJ
  

• 301 kJ
  

• 322.3 kJ
  

Which of the following is the definition of specific hest capacity?

• the amount of heat needed to taise the temp of a siubstance 100C

• The amount of heat needed to taise the temo of a substance 1C

• The amount of heat needed to taise the temp of a substance 10C

A chemical reaction is carried out in a closed container. The energy absorbed by the chemical reaction is 100 kJ. What is the energy liberated from the air or the walls of the container?

• 25 kJ

• 50 kJ

• 100 kJ

Which of the following measures thermal energy in an object?

• mass

• temperature

• heat

• volume

You have a series of four chemical reactions (1 → 2 → 3 → 4). How do you calculate the ΔH₂ if you know the other ΔH values?

• ΔH₂ = ΔH₄ – (ΔH₁ + ΔH₃)

• ΔH₂ = (ΔH₁)(ΔH₃)/(ΔH₄)

• ΔH₂ = ΔH₁ + ΔH₃ + ΔH₄

You have the following equations:

2S (s) + 3O ₂ (g) → 2SO ₃ (g), Δ H = –792 kJ

2S (s) + 2O ₂ (g) → 2SO ₂ (g), Δ H = –594 kJ

2SO ₂ (g) + O ₂ (g) → 2SO ₃ (g), Δ H = ?

What is the missing ΔH?

• -594 kJ

• -198 kJ

• +792 kJ

How much heat is given off when 16 g liquid methanol (CH₃OH) at its freezing point changes to solid methanol? (methanol ΔH_f = 3.16 kJ/mol)

• 0.36 kJ

• 1.58 kJ

• 0.79 kJ