Midterm 2 Review

Chapter 5

100

Calculate the number of moles of aluminum that will react with 3.18 mol oxygen to form aluminum oxide.

4Al(s) + 3O₂(g) → 2Al₂O₃(s)

4.24 mol Al

200

Calculate the molarity of each ion in each of the following solutions:

a) 0.344 M Al₂(SO₄)₃

b) 0.0808 M Ba(OH)₂

a) Al³⁺ = 0.688 M, SO₄^2- = 1.032 M

b) Ba²⁺ = 0.0808 M, OH^- = 0.1616 M

300

Calculate the concentration of an HCl solution if 25.00 mL HCl is titrated with 2.000 M NaOH. The initial buret reading is 2.17 mL, and the final buret reading is 39.42 mL.

2.980 M HCl

Chapter 6

100

Determine whether "w" is positive or negative in each scenario. The system is italicized.

a) A person is pedaling a bicycle down the street.

b) An elevator takes a person from the first floor of a building to the seventh floor.

a) The system (person) is doing work to the surrounding (bicycle), "w" is negative.

b) The surrounding (elevator) is doing work to the system (person), "w" is positive.

200

Calculate the specific heat of water if 83.68 J is required to raise the temperature of 4.000 g of water by 5.000°C.

c = 4.184 J/(g °C)

300

Use standard enthalpies of formation to find the enthalpy of reaction for the following equation:

CH₄(g) + 2O₂(g) → CO₂(g) + 2H₂O(l)

ΔH_f^o (kJ/mol): CH₄(g) = -74.81, CO₂(g) = -393.5, H₂O(l) = -285.8

–890.3 kJ/mol

Chapter 7

100

Calculate the pressure in atmospheres corresponding to:

a) 213.4 kPa

b) 743.9 torr

a) 2.106 atm

b) 0.9788 atm

200

Determine the molar mass of a gaseous substance if 11.4 g occupies 5.52 L at 1.10 atm and 12°C.

mm = 43.8 g/mol

300

Calculate the relative effusion rates of helium and oxygen gases.

Helium atoms effuse at a rate that is 2.83 times faster than the effusion rate of oxygen molecules.