AP Chemistry Unit 5

Which one shows the substances in the increasing order of their molar entropy?

• C(s) < H₂O(s) < H₂O(ℓ) < H₂O(g)
• H₂O(g) < H₂O(ℓ) < H₂O(s) < C(s)
• C(s) < H₂O(ℓ) < H₂O(g) < H₂O(s)
• C(s) < H₂O(g) < H₂O(ℓ) < H₂O(s)

Which of the following would probably have a positive ∆S value?

• 2 Ag(s) + Br2(ℓ) → 2 AgBr(s)
• H₂(g) + I₂(s) → 2 HI(g) 
• 2 NO₂(g) → N₂O₄(g)
• He(g, 2 atm) → He(g, 10 atm)

Which of the following has the smallest molar entropy at 298 K?

• Cl₂(g)
• Ne(g) 
• He(g) 
• N₂(g) 

A 100mL sample of water is placed in a coffee cup calorimeter.  Solid NaCl is then dissolved in the water.  The temperature of the water decreases from 20.5°C to 19.7°C and is then allowed to return to room temperature (20.5°C).  Determine the signs for ΔH and ΔS for the process of dissolving NaCl and 
ΔG for the entire process at constant temperature.

• +ΔH, −ΔS, ΔG=0
• −H, +S, ΔG=0
• +ΔH, +ΔS, −ΔG
• −ΔH, −ΔS, −ΔG

Tags

NGSS.HS-PS1-4

NGSS.HS-PS3-4

Consider the freezing of liquid water at −10°C and 1atm.  For this process, what are the signs for ΔH, ΔS, and ΔG?
NO Calculator!

• +ΔH, −ΔS, ΔG=0
• −H, +S, ΔG=0
• +ΔH, +ΔS, −ΔG
• −ΔH, −ΔS, −ΔG

Tags

NGSS.HS-PS3-2

NGSS.HS-PS3-4

Place the following in order of increasing entropy
NO Calculator!

• liqiud, solid, and gas
• gas, liqiud, and solid
• solid, liquid, and gas
• solid, gas, and liqiud

Tags

NGSS.MS-PS1-4

For the process H₂O(g) → H₂O(ℓ) at 1 atm and 100°C, the change in entropy is

• zero.
• negative.
• positive.

Tags

NGSS.HS-PS3-4

CuO(s) → Cu(s) + ½O₂(g) 
∆G°=128kJ/mol
Predict and justify the sign of ∆S° for the reaction.

• ∆S is positive because ∆G is positive.
• ∆S is negative because ∆G is positive.
• ∆S is positive because the products have more moles of gas than the reactants.
• ∆S is negative because the products have more moles of gas than the reactants.

Consider the equation
NH₄Br(s) → NH₃(g) + HBr(g)
carefully, and think about the sign of ∆S for the reaction it describes. ∆H = +188.3 kJ. Which response describes the thermodynamic spontaneity of the reaction?

• The reaction is spontaneous at all temperatures.
• The reaction is spontaneous only at relatively high temperatures.
• The reaction is spontaneous only at relatively low temperatures.
• The reaction is not spontaneous at any temperatures. 

2CuO(s) + C(s) → 2Cu(s) + CO₂(g)
ΔG°=-266kJ/mol
Which statement is correct about the value of K for the reaction above at standard conditions?

• K will be less than 0.
• K will be 0.
• K will be greater than 1.
• K will be between 0 and 1.

Tags

NGSS.HS-PS1-4