Free Printable Chemical Thermodynamics

1.

Benjamin, Avery, and Anika are discussing the entropy change ( $\Delta S$ ) for different processes. For which of these processes is the value of $\Delta S$ expected to be negative?
I. Benjamin dissolves NaCl in water.
II. Avery condenses steam into liquid water.
III. Anika decomposes $MgCO_3$ into MgO and $CO_2$ .

a)

I only

b)

I and III only

c)

II only

d)

II and III only

2.

Kai is using a commercial chemical cold pack for a science experiment. He breaks an inner pouch containing water and allows it to mix with a sample of solid ammonium nitrate. The signs of the values for $\Delta H$ and $\Delta S$ for the dissociation reaction must be, respectively

a)

Positive, positive

b)

Positive, negative

c)

Negative, positive

d)

Negative, negative

3.

Aria, Charlotte, and Zoe are studying for their physics exam. They come across a question about the 3rd Law of Thermodynamics. They understand that it indicates that

a)

the enthalpy of a hot cup of coffee they are sharing is a constant

b)

the entropy of their messy study room increases

c)

the sum of the entropies of their textbooks and the surrounding room is zero

d)

the entropy of a perfectly ordered pure crystal they are studying is zero at absolute zero

4.

Zoe, Abigail, and Kai were discussing about the 1st Law of Thermodynamics in their physics class. According to their discussion, the 1st Law of Thermodynamics indicates that

a)

work is force exerted over a distance, like when Kai pushes a heavy box.

b)

energy in the universe is finite, similar to the limited amount of gasoline in Zoe's car.

c)

an increase in disorder is part of any spontaneous process, like when Abigail's room gets messy.

d)

work is a state function, like the constant state of energy in their classroom.

5.

Ethan, Sophia, and Maya are studying for their chemistry exam. They are discussing the concept of entropy and its changes during different processes. They come across a question: For which of the following processes will $\Delta S$ be negative?

a)

$PbCl_2\left(s\right)\rightarrow Pb^{2+}\left(aq\right)+2Cl^-\left(aq\right)$ (Ethan's experiment of dissolving Lead(II) chloride in water)

b)

$MgO\left(s\right)+\ CO_2\left(g\right)\rightarrow MgCO_3\left(s\right)$ (Sophia's experiment of reacting Magnesium oxide with Carbon dioxide)

c)

$CO_2\left(aq\right)\rightarrow CO_2\left(g\right)$ (Maya's experiment of releasing Carbon dioxide from soda)

d)

$C_5H_{12}\left(l\right)\ +\ 8O_2\left(g\right)\longrightarrow\ 5CO_2\left(g\right)\ +\ 6H_2O\left(g\right)$ (Ethan's experiment of burning Pentane in air)

6.

During a chemistry class, Charlotte, Nora, and Abigail were discussing the entropy of different substances. They were trying to figure out which substance has the smallest value for $S\degree$ . They narrowed it down to the following options:

a)

$AlCl_3$

b)

$MgCl_2$

c)

$NaCl$

d)

$SnCl_4$

7.

Oliver, Lily, and Liam are conducting a science experiment. They are trying to determine which of the following substances would have the largest standard molar entropy if they were to use it in their experiment. Can you help them?

a)

$H_2O\left(l\right)$

b)

$H_2O\left(g\right)$

c)

$H_2O_2\left(l\right)$

d)

$H_2O_2\left(g\right)$

8.

Ethan, Evelyn, and Grace are working on a chemistry project. They are asked to calculate the standard entropy (in kJ) of reaction at 25 °C for the following reaction they are conducting in their lab.

N₂(g) + 3H₂(g) → 2 NH₃(g)

The standard molar entropies (J/mol•K) of N₂, H₂, and NH₃ are 191.5 , 130.6, and 192.3, respectively.

a)

+1987 kJ/mol.K

b)

-1987 kJ/mol.K

c)

-0.1987 kJ/mol.K

d)

+0.1987 kJ/mol.K

9.

Evelyn, Lily, and Olivia are studying for their chemistry exam. They come across a problem where they need to calculate the ΔG˚ (in kJ/mol) for the reaction given below if ΔH˚ and ΔS˚ are -196 kJ/mol and -191 J/mol.K, respectively.

2 SO₂ (g) + O₂ (g) $\rightarrow$ 2 SO₃ (g)

They remember the formula ΔG˚ = ΔH˚ - T ΔS˚. What is the ΔG˚ for this reaction?

a)

+139 kJ/mol

b)

-139 kJ/mol

c)

+0.139 kJ/mol

d)

-0.139 kJ/mol

10.

Anika, James, and Noah are studying for their chemistry exam. They come across a question about chemical equilibrium. They want to know the equilibrium constant for a reaction they conducted in their school lab at 25 °C, where they found ΔG˚ to be -139 kJ/mol. They remember the formula:

k = e^-ΔG/RT

^{where R = 8.314 J/mol.K}

Can you help them find the equilibrium constant?

a)

$2.39\times10^{24}$

b)

2.39

c)

$2.39\times10^{-24}$

d)

$3.29\times10^{24}$

Chemical Thermodynamics_I

Total questions: 10

Worksheet time: 5mins

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