Homework Answers

If I prepare a solution by adding 25 mL of 2.0 M NaOH into a 500 mL volumetric flask, and filling the flask to the mark with water, what will the final concentration of the solution be? [1] 0.05 M

[2] 0.1 M

[3] 0.5 M

[4] 2.0 M

[5] 40.0 M 

Suppose that a solution is prepared by mixing 25 mL (0.22 mol, 16 g) of pentane (the solute) with 45 mL (0.34 mol, 30 g) of hexane (the solvent). If the volumes add on mixing,

What is the mole fraction of the pentane?

[1] 0.35

[2] 0.39

[3] 0.64

[4] 39%

[5] 64 % 

Suppose that a solution is prepared by mixing 25 mL (0.22 mol, 16 g) of pentane (the solute) with 45 mL (0.34 mol, 30 g) of hexane (the solvent). If the volumes add on mixing,

Calculate the molarity of the pentane?

[1] 3.1 mol/kg

[2] 7.3 mol/kg

[3] 3.1 mol/L

[4] 7.3 mol/L

[5] 45.8 mol/L

Suppose that a solution is prepared by mixing 25 mL (0.22 mol, 16 g) of pentane (the solute) with 45 mL (0.34 mol, 30 g) of hexane (the solvent). If the volumes add on mixing.

Calculate the molality of the pentane

[1] 3.1 mol/kg

[2] 4.8 mol/kg

[3] 7.3 mol/kg

[4] 3.1 mol/L

[5] 7.3 mol/L 

The value of a solution concentration unit that may change with temperature is

[1] molarity.

[2] mole fraction.

[3] molality.

[4] mole percentage.

[5] weight percentage.

Suppose that the actual moles of MgO produced was 0.5 mol, what is the percentage yield of MgO?

[1] 0.62%

[2] 1.2%

[3] 10%

[4] 25%

[5] 50%

Calculate how many moles of the excess reagent remain unreacted.

[1] 1 mol

[2] 2 mol

[3] 4 mol

[4] 5 mol

[5] No excess reagent remains unreacted