AP Chemistry - Thermodynamics

For which of these processes is the value of  $\Delta S$  expected to be negative?
I. NaCl is dissolved in water.
II. Steam condenses to liquid water.
III.  $MgCO_3$   is decomposed into MgO and  $CO_2$  .

• I only

• I and III only

• II only

• II and III only

Tags

NGSS.HS-PS3-4

The endothermic process among the following is

• Natural gas is combusted in a Bunsen burner.

• Water vapor condenses on the outside of a glass of iced tea.

• A cop of hot water cools as a tea bag brews.

• An ice cube melts on a countertop.

Tags

NGSS.MS-PS1-4

NGSS.MS-PS3-4

In a commercial chemical cold pack, an inner pouch containing water is broken and the water is allowed 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

• Positive, positive

• Positive, negative

• Negative, positive

• Negative, negative

Tags

NGSS.HS-PS1-4

The 3rd Law of Thermodynamics indicates that

• enthalpy of the universe is a constant

• entropy of the universe increases

• sum of the entropies of the system plus surroundings is zero

• entropy of a perfectly ordered pure crystal is zero at absolute zero

The 1st Law of Thermodynamics indicates that

• work is force exerted over a distance.

• energy in the universe is finite.

• an increase in disorder is part of any spontaneous process.

• work is a state function.

Entropy of the universe is

• always zero.

• always constant.

• always increasing.

• always decreasing.

Tags

NGSS.HS-PS3-4

A process which causes a decrease in the entropy is

• condensation of steam to form liquid water.

• vaporization of liquid water to form steam.

• dissociation of solid sodium chloride into aqueous sodium cations and chloride anions

• sublimation of snow to water vapor.

For which of the following processes will $\Delta S$  be negative?

•  $PbCl_2\left(s\right)\rightarrow Pb^{2+}\left(aq\right)+2Cl^-\left(aq\right)$  

•  $MgO\left(s\right)+\ CO_2\left(g\right)\rightarrow MgCO_3\left(s\right)$  

•  $CO_2\left(aq\right)\rightarrow CO_2\left(g\right)$  

•  $C_5H_{12}\left(l\right)\ +\ 8O_2\left(g\right)\longrightarrow\ 5CO_2\left(g\right)\ +\ 6H_2O\left(g\right)$  

The substance with the smallest value for $S\degree$  is

•  $AlCl_3$  

•  $MgCl_2$  

•  $NaCl$  

•  $SnCl_4$  

Which of the following substances is expected to have the largest standard molar entropy?

• $H_2O\left(l\right)$

• $H_2O\left(g\right)$

• $H_2O_2\left(l\right)$

• $H_2O_2\left(g\right)$