Solutions Chemistry Practice Test Part 2

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A solution is prepared from 0.0200 mol of hexane and 0.0300 mol of isopropanol. Assuming the solution is ideal; calculate the vapor pressure at 25^oC. (Vapor pressure of hexane = 150.0 torr; vapor pressure of isopropanol = 44 torr at 25^oC).

4.32 torr

86.4 torr

107.6 torr

92.2 torr

74.5 torr

The actual vapor pressure of the sol’n in question 3 was determined to be 92.3 torr. According to Raoult’s law this solution exhibits:

Positive deviation

Negative deviation

Hydrophobic deviation

Hydrophilic deviation

Ideal deviation

When 236.0 mL of 0.830 M HCl is diluted with 141.0 mL of water, the molarity of the solution (assuming volumes are additive) is

0.310 M

0.00220 M

0.520 M

1.39 M

0.128 M

Seawater contains 1.94% chlorine (by mass). How many grams of chlorine are there in 400 mL of seawater if the density of seawater is 1.025 g/cm³.

What concentration of sodium chloride in water is needed to produce an aqueous solution isotonic with blood (∏ = 7.7 atm at 25°C)?

A solution contains 1 mol of liquid A and 3 mol of liquid B. The vapor pressure of this solution is 314 torr at 25^oC. At 25^oC, the vapor pressure of liquid A is 265 torr and the vapor pressure of liquid B is 355 torr. Which of the following is true?

This solution exhibits a positive deviation from Raoult’s Law.
This solution exhibits a negative deviation from Raoult’s Law.
This solution is ideal.

0.9 moles of CH₂Cl₂ and 7.5 moles of CH₂Br₂ combine to form an ideal solution. At 25^oC, the vapor pressure of pure CH₂Cl₂ is 133 torr and the vapor pressure of pure CH₂Br₂ is 11.4 torr. Calculate the mole fraction of CH₂Cl₂ in the vapor phase at 25^oC.

0.11

0.42

0.58

0.89

None of these

Would you expect a mixture of (C₃H₆O) and water to increase, decrease or maintain temperature?

If a solution has a positive deviation from Raoult’s law, how would the boiling point change, if at all?

Given:

1.5M KI, 1.0M NaCl, 2.0M HNO₂, 2.0M NaBr, 1.5M CaCl₂

Which solution would have the

Lowest freezing point?

Highest boiling point?

Greatest Vapor pressure?

The freezing point (T_f) for t-butanol (C₄H₉OH) is 25.50^oC, and K_f is 9.1^oC/m. Usually t-butanol absorbs water on exposure to the air. If the freezing point of a 13.7 g sample of t-butanol is measured at 24.89^oC, how many grams of water are present in the sample?

0.022 g

0.017 g

0.20 g

0.80 g

7.3 g

When the vapor pressures reach equilibrium for the following

The volumes are equal.

Beaker A is empty

Beaker B is empty

Greater volume in A than B.

Greater volume in B than A.

A solid mixture contains MgCl₂ (molar mass = 95.218 g./mol) and NaCl (molar mass = 58.443 g/mol). When 0.5000 g of this solid is dissolved in enough water to form 1.000 L of solution, the osmotic pressure at 25.0^oC is observed to be 0.3950 atm. What is the mass percent of MgCl₂ in the solid (assume ideal behavior for sol’n).

A 1.60 g sample of a mixture of naphthalene (C₁₀H₈) and anthracene (C₁₄H₁₀) is dissolved in 20.0 g of benzene (C₆H₆). The freezing point of the solution is is 2.81^oC. What is the composition of the sample mixture in terms of mass percent? The freezing point of benzene is 5.51^oC and K_f is 5.12 ^oC kg/mol.

An open beaker of saline solution is left out on your lab bench. The vapor pressure of the solution would __________ as time proceeded.

Increase

Decrease

Remain the same

The vapor pressure of carbon tetrachloride CCl₄, is 0.354 atm and the vapor pressure of chloroform, CHCl₃, is 0.526 atm at 316 K. A solution is prepared from equal masses of these two compounds at this temperature. Calculate the mole fraction of the chloroform in the vapor above the solution. If the vapor above the original solution is condensed and isolated into a separate flask, what would the vapor pressure of chloroform be above this new solution?

The term proof is defined as twice the percent by volume of pure ethanol in solution. Thus, a solution that is 95% (by volume) ethanol is 190 proof. What is the molality of ethanol in a 92 proof ethanol/water solution?

Density of ethanol                                     0.80 g/cm³

Density of water                             1.0 g/cm³

Molecular wt. of ethanol                         46 g/mol

True or False: We can predict the solubility of a compound by looking at the sign of the enthalpy of solution.

Which of the following statements is(are) true?

The rate of dissolution of a solid in a liquid always increases with increasing temperature.

The solubility of a solid in a liquid always increases with increasing temperature.

According to Henry's law, the amount of gas dissolved in a solution is directly proportional to the pressure of the gas above the liquid.

Two of these statements are true.

All of these statements are true.

For each of the following solutions, would you expect it with respect to Raoult's law to be relatively ideal, to show a positive deviation, or to show a negative deviation?

hexane (C₆H₁₄) and chloroform (CHCl₃)

water and acetone (C₃H₆O)

hexane (C₆H₁₄) and octane (C₈H₁₈)

When a nonvolatile solute is added to a volatile solvent, the solution vapor pressure __________, the boiling point __________, the freezing point __________, and the osmotic pressure across a semi-permeable membrane __________.

A 0.2 molar solution of a solute X, in benzene, displays an osmotic pressure given by the formula  = (0.1)RT. Which of the following is most likely to be the case?

X exists in benzene as X.

X exists in benzene as X_2.

X exists in benzene dissociated into two particles.

This solution strongly deviates from ideal behavior.

If the human eye has an osmotic pressure of 8.45 atm at 25°C, what concentration of solute particles in water will provide an isotonic solution?

0.346 M

4.11M

3.49 x 10^-3 M

4.04 x 10^-2 M

0.673 M

The solubility of the salt M_xA_y is 1.0  10^-2 mol/L at 25°C. The osmotic pressure exhibited by a solution saturated with M_xA_y at 25°C is 1.22 atm. Determine the values of x and y by assuming ideal behavior.

x = 1, y =3
x = 2, y = 5
x = 2, y = 3
x = 1, y = 1

What is the molar mass of glucose if 22.5 g gives a freezing point of –0.930°C when dissolved in 250.0 g of water? If the empirical formula is CH₂O, what is the molecular formula? (K_f=1.86 C kg/mol)

An aqueous solution is 1.00% NaCl by mass. Its density is 1.071 g/mL at 25°C. The observed osmotic pressure of this solution is 7.83 atm at 25°C.

What fraction of the moles of NaCl in this solution are ion pairs?

Calculate the freezing point that would be observed for this solution; K_f for H₂O = 1.86° C kg/mol.

In the vapor over a pentane – hexane solution at 25^oC, the mole fraction of pentane is equal to 0.15. What is the mole fraction of pentane in the solution? The vapor pressure of pure pentane and hexane are 511 and 150. torr respectively.

Which of the following aqueous solutions is expected to have the largest Van’t Hoff factor?

0.10 m I₂

0.10 m NaCl

0.10 m K₂SO₄

0.01 m K₂SO₄

For which of the following solutions would one be most likely to expect a positive deviation from Raoult’s Law?

Octane and 1-butanol

Propanone and water

Pentanal and ethanoic acid

More than one of these

None of these

An aqueous solution contains 0.250 moles of Q, a strong electrolyte, in 5.00 x 10² g of water freezes at -2.79 ^oC. What is the van’t Hoff factor for Q? The molal freezing point depression constant for water is 1.86 ^oC kg/mol. What is the formula of Q if it is 38.68% chlorine by mass and there are twice as many anions as cations in one molecule.

You have a solution of two volatile liquids, A and B (assume ideal behavior). Pure liquid A has a vapor pressure of 350.0 torr and pure liquid B has a vapor pressure 100.0 torr at the temperature of the solution. The vapor at equilibrium above the solution has double the mole fraction of substance A as the solution does. What is the mole fraction of liquid A in the solution?