Question

# Please answer the following questions! (6pts) Sketch each of the crystal cell types below, and note...

(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 25oC, 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 kCO2 = 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 25.0oC.

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. CaCl2   ______________       ________

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