1. Equilibrium

2SO3(g) <--> O2(g) + 2SO2(g)
A 3.21g sample of sulfur trioxide is placed in a 2.25 L cylinder and allowed to reach equilibrium at a constant temperature of 500 , as shown in the above equation. Analysis shows 1.23 X 10^-2 mol of sulfur dioxide at equilibrium.
a. Write the equilibrium constant expression (Kc) for this system.
b. Calculate the concentration of all three gases at equilibrium.
c. Calculate the Kc value for this system.
d. Calculate the value of Kp at this same temperature.

I know the answer to a. is Kc = [O2][SO2]^2/[So3]^2
I don't know about b,c, or d.

2.
a. Ammonia gas is added to boron trichloride gas.
Identify the Lewis acid in this reaction.
b. Potassium oxide solid is added to water. What is the expected pH of the solution.
c. Concentrated ammonia solution is added to copper (II) nitrate solution. How might the product be identified?

3. Explain the following observations:
a. WHen a solid is heated at its melting temperature, the temperature does not increase.
b. The melting temperature of KCl is less than that of NaF.
c. Liquid bromine and ICl have almost the same molecular mass, but ICl boils at a temperature 40 degrees Celsius higher than Br2.
d. The boiling temperature of HCl is lower that that of HF.
e. When alcohol (ethanol) is poured over your arm, your skin feels cold.

It is best to post a single question. Here you have three questions with multiple parts for a total of about 13 questions. We will get to them one by one.

1. Equilibrium
2SO3(g) <--> O2(g) + 2SO2(g)
A 3.21g sample of sulfur trioxide is placed in a 2.25 L cylinder and allowed to reach equilibrium at a constant temperature of 500 , as shown in the above equation. Analysis shows 1.23 X 10^-2 mol of sulfur dioxide at equilibrium.
a. Write the equilibrium constant expression (Kc) for this system.
b. Calculate the concentration of all three gases at equilibrium.
(SO2) = mols SO2/Liters.
(O2) = 1/2 (SO2)
(SO3) = [(mols SO3 initially)-mols SO2 at equilibrium)]/Liters.


c. Calculate the Kc value for this system.
Plug values from part b into your answer for part a and calculate Kc.

d. Calculate the value of Kp at this same temperature.
Look up the equation for converting Kc to Kp and calculate
Your answer to a is correct

2.
a. Ammonia gas is added to boron trichloride gas.
Identify the Lewis acid in this reaction.

Draw the Lewis electron dot structure for NH3 and for BF3. Look to see which molecule gives the electrons and which molecule receives the electrons. Remember that a Lewis acid is an electron acceptor.


b. Potassium oxide solid is added to water. What is the expected pH of the solution.
What is the equation? Oxides of group IA and IIA metals react with water to form bases.

c. Concentrated ammonia solution is added to copper (II) nitrate solution. How might the product be identified?

It all depends upon how much NH3 is added. Just a small amount will produce a precipitate of Cu)OH)2. More NH3 will produce Cu(NH3)4^+2 which is a complex ion that has a deep blue/purple color.


3. Explain the following observations:
a. WHen a solid is heated at its melting temperature, the temperature does not increase.
b. The melting temperature of KCl is less than that of NaF.
c. Liquid bromine and ICl have almost the same molecular mass, but ICl boils at a temperature 40 degrees Celsius higher than Br2.
d. The boiling temperature of HCl is lower that that of HF.
e. When alcohol (ethanol) is poured over your arm, your skin feels cold.

These are thought questions. Post your thoughts and someone will critique them.

a. When a solid is heated at its melting temperature, the temperature does not increase because the energy being supplied is being used to overcome the intermolecular forces holding the solid together rather than increasing the kinetic energy of the particles.

b. The melting temperature of KCl is less than that of NaF because KCl has weaker intermolecular forces than NaF. KCl is composed of K+ and Cl- ions, which have weaker electrostatic attractions compared to the Na+ and F- ions in NaF.

c. Liquid bromine and ICl have almost the same molecular mass, but ICl boils at a temperature 40 degrees Celsius higher than Br2 because ICl has stronger intermolecular forces than Br2. ICl has dipole-dipole interactions due to the polar bond between iodine and chlorine, while Br2 only has London dispersion forces.

d. The boiling temperature of HCl is lower than that of HF because HF has stronger intermolecular forces than HCl. HF has hydrogen bonding, resulting in stronger attractions between molecules, while HCl only has dipole-dipole interactions.

e. When alcohol (ethanol) is poured over your arm, your skin feels cold because evaporation is an endothermic process. As the alcohol evaporates off your skin, it absorbs heat from your skin, causing a cooling sensation.

For the first question:

b. To calculate the concentrations of all three gases at equilibrium, we need to use stoichiometry and the given information. From the balanced equation, we can determine that the molar ratio between SO3 and SO2 is 1:2. So, if we have 1.23 x 10^-2 mol of SO2, then we would have twice that amount of SO3, which is 2 x 1.23 x 10^-2 = 2.46 x 10^-2 mol. The concentration of SO3 would be (2.46 x 10^-2 mol) / (2.25 L) = 1.09 x 10^-2 M.

To find the concentration of O2, we use the balanced equation and stoichiometry. The molar ratio between SO3 and O2 is 1:1. So, the concentration of O2 would be the same as the concentration of SO3, which is 1.09 x 10^-2 M.

c. To calculate the Kc value for this system, we use the equilibrium expression: Kc = [O2][SO2]^2 / [SO3]^2. Plugging in the values we found in part b, we have Kc = (1.09 x 10^-2)^2 / (1.09 x 10^-2)^2 = 1.

d. To calculate the value of Kp at the same temperature, we need to use the equation: Kp = Kc(RT)^(Δn), where Δn is the difference in moles between the products and reactants. In this case, the Δn value is 1 - 2 = -1, since there is one less mole of gas on the product side. Plugging in the values, we have Kp = 1(0.0821 L.atm/mol.K)(500 K)^(-1) = 0.016 atm.

a. When a solid is heated at its melting temperature, the temperature does not increase because the heat energy is being used to overcome the intermolecular forces holding the solid together and convert it into a liquid. This energy is known as the heat of fusion.

b. The melting temperature of KCl is less than that of NaF because the ionic bond in KCl is weaker than the ionic bond in NaF. This is because K+ ion is larger and has a lower charge density compared to Na+ ion. The lower charge density means that the attractive forces between the positive and negative ions in KCl are weaker, making it easier to overcome and melt the solid.

c. Liquid bromine and ICl have almost the same molecular mass, but ICl boils at a temperature 40 degrees Celsius higher than Br2 because ICl molecules have stronger intermolecular forces than Br2 molecules. This is due to the presence of a polar covalent bond in ICl, which leads to dipole-dipole interactions between the molecules. These dipole-dipole interactions are stronger than the London dispersion forces between Br2 molecules, resulting in a higher boiling point for ICl.

d. The boiling temperature of HCl is lower than that of HF because HF molecules have stronger intermolecular forces than HCl molecules. This is due to hydrogen bonding between the HF molecules. Hydrogen bonding is a special type of dipole-dipole interaction, where a hydrogen atom bonded to a highly electronegative atom (in this case, fluorine) is attracted to another electronegative atom (in this case, another fluorine atom). This leads to stronger intermolecular forces in HF, requiring more energy to break the bonds and reach the boiling point.

e. When alcohol (ethanol) is poured over your arm, your skin feels cold because alcohol evaporates quickly, and the process of evaporation is endothermic. As the alcohol molecules evaporate from the surface of your skin, they take away heat energy from your skin, causing the cooling sensation. This is similar to the process of sweating, where the evaporation of sweat from your skin helps to cool you down.