Question

Please answer the following questions!

(6pts) Sketch each of the crystal cell types below, and note how many atoms there are per unit cell.

# atoms/unit cell

Face-centered cubic                        ______

Simple cubic                            ______

Body-centered cubic                        ______

(3pts) If 2.29 grams of formaldehyde, H₂CO, are added to 100.0 g of water, we are told the total volume of the solution is 102.0 mL. Given the molar mass of formaldehyde = 30.0g. Calculate the molarity (M) of the solution.

Ans._____________________

3. A gas mixture contains 25.1 g of carbon monoxide (CO) and 46.8 g of carbon dioxide (CO₂).

a. (2pts) How many moles of each gas are present?

                                   # Moles CO = __________

# Moles CO₂ = _________

b. (1pt) What is the mole fraction of carbon monoxide?

Ans.____________________

c. (1pt) What is the mole fraction of carbon dioxide?

Ans.____________________

4.   A bottle of soda is opened and allowed to equilibrate at 25^oC, under a partial pressure of 2.6 x 10^-4 atm.

a. (1pt) Calculate the concentration, in moles/L, of CO₂ in the drink. Given k_CO2 = 3.4 x 10^-2 atm/(mol/L)

Ans.____________________

b. (1pt) If the partial pressure were lower, would you expect the concentration of carbon dioxide in the soda to be higher or lower than the above result? Explain.

_____________________________________________________________________

5. The osmotic pressure of an aqueous solution with a molecular solute = 0.350 atm.

a. (1pt) Calculate the molarity of the solution, if the pressure were measured at 25.0^oC.

Ans.____________________

b. (2pts) If this is a sucrose (C₁₂H₂₂O₁₁ )solution, with M = 0.0140, how many grams of sucrose would dissolve in 250mL of water? Note: molar mass of sucrose = 342g.

Ans.__________________

6. (2pts) Note the individual particles and the theoretical van ‘t Hoff factor i for:

       Particles       # of particles

a. KCl       ___________       ________

b. CaCl_{2   _________}_____       ________

Thank you!

Answer 1