AP Chemistry Unit 8

Using the equations below: C(s) + O₂(g) → CO₂(g) ∆H = –390 kJ Mn(s) + O₂(g) → MnO₂(s) ∆H = –520 kJ what is ∆H (in kJ) for the following reaction? MnO₂(s) + C(s) → Mn_(s) + CO₂(g)

• 910

• 130

• -130

• -910

Tags

NGSS.HS-PS1-4

Using the equations below Cu(s) + 1/2O2(g) → CuO(s) ∆H = –156 kJ 2Cu(s) + O2(g) → Cu2O(s) ∆H = –170 kJ what is the value of ∆H (in kJ) for the following reaction? 2CuO(s) → Cu2O(s) + 1/2O2(g)

• 142

• 15

• -15

• -142

Tags

NGSS.HS-PS1-4

Which of these processes represents a decrease in entropy?

• sublimation of CO₂

• boiling water

• condensation of steam on cold glass

• NaCl dissolving in water

Which of these reactions shows a DECREASE in entropy?

• CaCO₃(s) → CaO(s) + CO₂(g)

• 3O₂(g) → 2O₃(g)

• 2NH₃(g) → 3H₂(g) + N₂(g)

• C₆H₆(l) → C₆H₆(g)

A reaction has a positive ΔH and a positive ΔS. Which of the following is true?

• It will be spontaneous at all temperatures.

• It will be nonspontaneous at all temperatures.

• It will be spontaneous at low temperatures.

• It will be spontaneous at high temperatures.

Your enthalpy is high and negative but your entropy is also negative. What type of temperature would you want to get a spontaneous reaction?

• low

• high

Which combination of ΔH and ΔS NEVER has a spontaneous reaction?

• +ΔH and +ΔS

• +ΔH and -ΔS

• -ΔH and -ΔS

• -ΔH and +ΔS

True/False: The rate of a chemical reaction is unrelated to the spontaneity of the reaction.

• True

• False

Calculate the standard entropy change for the following reaction: Cu(s)+1/2 O₂(g) → CuO(s). Given that S⁰ (Cu(s)) = 33.15 J/K*mol S⁰ (O₂(g)) = 205.14 J/K*mol S⁰ (CuO(s)) = 42.5 J/K*mol

• 195.66 J/K.mol

• 93.09 J/K.mol

• -93.09 J/K.mol

• +195.66 J/K.mol

Tags

NGSS.HS-PS3-1

In the reaction pictured, how many moles of hydrogen will be formed when 4 mol of HCl are consumed?

• 6

• 4

• 2

• 8

Tags

NGSS.HS-PS1-7