1/ As a warm up, calculate the mass percent, molality, mole fraction of solute,

ID: 880471 • Letter: 1

Question

1/ As a warm up, calculate the mass percent, molality, mole fraction of solute, and normality of a 1.37M aqueous citric acid solution ( which has three acidic protons) if the density of the solution is 1.10 g/cm^3 and the molecular formula of citric acid is H3C6H5O7.

2/ The vapor pressure of a solution containing 53.6 grams of glycerin (C3H8O3) in 133.7 grams of ethanol (C2H5OH) is 113 torr at 40*Celcius . Calculate the vapor pressure of pure ethanol at 40*C assuming that glycerin is a nonvolatile, nonelectrolyte solute in ethanol.

3/ A solution is prepared by dissolving 50 grams of sucrose (C12H22O11) in 225 grams of water calculate the boiling point and freezing point of this solution.

4/Blood has an average osmotic pressure of 5,852 torr at 37*Celcius. Determine the molar concentration of glucose (C6H12O6) that will be isotonic with blood at 37*C.

5/ A 4.367 gram sample of a hydrocarbon is dissolved in 21.35 grams of benzene. The freezing point of the solution is -0.51*C. The freezing point of pure benzene is 5.50*C and Kf of benzene is 5.12*C . kg/mol. Determine to molar mass of the hydrocarbon.

6/2.50 grams of iron (III) sulfate is dissolved in 575 grams of water. Calculate the freezing point and boiling point of the solution. Assume that the solute completely dissociates.

7/ How many Moles of water are formed when one mole of Pentane, C5H12 combusts completely?

8/ What would Happen to a closed sample of a gas whose temperature is increased while its volume is decreased ?

A/ It's pressure would decrease

B/ It's pressure would increase

C/ its pressure would remain constant

D/ The number of moles of the gas would decrease

9/ Which of the following is not an assumption of the kinetic molecular theory for a gas?

A/ Gases are made up of tiny particles in constant chaotic motion.

B/ Gas particles are very small compared to the average distance between the particles.

C/ Gas particles collide with the walls of their container in elastic collisions.

D/ Gas particles have an average velocity that is directly proportional to their absolute temperature.

10/ Consider the reaction H2(g) + .5O2(g) ----> H2O(I) H*= -286 Kj

which of the following is true?

A/ The reaction is exothermic

B/ The reaction is endothermic

C/ The enthalpy of the products is less than that of the reactants.

D/ Heat is absorbed by the system

E/ The reaction is exothermic and the enthalpy of the products is less than that of the reactants.

11/ the total volume of hydrogen gass needed to fill the Hindenburge was 2x10^8 liters at 1 atm and 25*C. How Much energy was evolved when it burned ?

H2(g) + .5O2(g) ----> H2O(I) H* = -286Kj

12/ The heat of formation of iron(III) oxide is -826KJ/mol. Calculate the heat of the reaction when a 55.8 g sample of iron is reacted with an excess of oxygen gas.

4Fe(s) + 3O2(g) -----> 2Fe2O3(s)

13/ Given the following reactions and H values,

2N2O(g) ----> O2(g) + 2N2(g) H = -164 KJ

2NH3(g) + 3N2O(g) ----> 4N2(g) + 3H2O(I) H = -1012 KJ

Calculate H for 4NH3(g) + 3O2(g) -----> 2N2(g) + 6H2O(I)

14/ what is the molality of a solution of 50 grams of propanol C3H8O in 152ml of water, If the density of water is 1g/ml ?

15/ 2.5 liters of aqueous solution containing 50 grams of Mgcl2 dissolved in pure water is prepared. The molarity of the solution is ?

16/ the vapor pressure of water at 25*Celcius is 23.8 torr. Determine the mass of glucose( molar mass= 180g/mol) needed to add to 500 grams of water to change the vapor pressure to 23.1 torr.

17/ A Cucumber is placed in a concentrated salt solution. What will most likely happen?

A/ Water will flow form the cucumber to the salt solution.

B/ Water will flow form the solution to the cucumber

C/ Salt will flow into the container.

D/ Salt will precipitate out of the solution.

18/ When a water molecule forms a hydrogen bond with another water molecule, Which atoms are involved in the interaction?

A/ A hydrogen form one molecule and a hydrogen form the other molecule

B/ A hydrogen form one molecule and an oxygen form the other molecule

C/ An oxygen form one molecule and an oxygen form the other molecule

D/ Two hydrogens form one molecule and one oxygen form the other molecule.

Explanation / Answer

The solutions are as follows.

1. 1/ As a warm up, calculate the mass percent, molality, mole fraction of solute, and normality of a 1.37M aqueous citric acid solution ( which has three acidic protons) if the density of the solution is 1.10 g/cm^3 and the molecular formula of citric acid is H3C6H5O7.

Molarity of solution = 1.37 M

molar mass of Citric acid = 192.12 g/mol

Molality = 1.37/1.10 = 1.25 molal

g of citric acid = 1.37 x 192.12 = 263.2044 g

mass of water = 736.80 g

mass % of citric acid = 263.2044/1000g = 26.32 %

Normality = 1.37 x 3 = 4.11 N

Moles glycerin = 53.6 g /92 g/mol =0.582

Moles ethanol = 133.7 g /46 g/mol =2.91

total moles = 3.492

Moles fraction ethanol = 2.91 / 3.492 =0.833

p = p° X

113 = p° 0.833

p° = 135.6 torr

3/ A solution is prepared by dissolving 50 grams of sucrose (C12H22O11) in 225 grams of water calculate the boiling point and freezing point of this solution.

molality of solution = 50/0.225 x 342.30 = 0.65 molal

delta Tb = mkb = 0.65 x 0.512 = 0.33 oC

delta Tf = 0.65 x 1.86 = 1.21 oC

4/Blood has an average osmotic pressure of 5,852 torr at 37*Celcius. Determine the molar concentration of glucose (C6H12O6) that will be isotonic with blood at 37*C.

osmotic pressure = iMRT

Osmotic pressure is expressed by the formula:

where
i = van 't Hoff factor of the solute = 1
M = molar concentration in mol/L
R = universal gas constant = 0.08206 L·atm/mol·K

concentration of glucose

M = 0.08206 x (273 + 37)/7.7 atm = 0.303 M

Calculate amount of sucrose per liter

M = mol/Volume

mol = M·Volume

mol = 0.303 mol/L x 1 L

mol = 0.303 mol

molar mass of glucose = 180 g/mol

mass of glucose = 0.303 mol x 180 g/1 mol

mass of glucose = 54.54 g

Thus, answer is 54.54g

deltaTf = -Kfm

5.12 + 0.51 = 5.12 x 4.367/molar mass x 0.02135

molar mass = 5896.08 g/mol

6/2.50 grams of iron (III) sulfate is dissolved in 575 grams of water. Calculate the freezing point and boiling point of the solution. Assume that the solute completely dissociates.

molality of iron(III)sulfate = 2.50/0.575 x 399.88 = 0.0109 molal

delta Tb = 5 x 0.0109 x 0.512 = 0.028 oC

delat Tf = iKfm = -5 x 1.86 x 0.0109 = -0.10 oC

7/ How many Moles of water are formed when one mole of Pentane, C5H12 combusts completely

C5H12 + 8 O2 = 5 CO2 + 6 H2O

1 mole of C5H12 produces 6 moles of H2O

8/ What would Happen to a closed sample of a gas whose temperature is increased while its volume is decreased,

B/ It's pressure would increase

9/ Which of the following is not an assumption of the kinetic molecular theory for a gas,

D/ Gas particles have an average velocity that is directly proportional to their absolute temperature.

10/ Consider the reaction H2(g) + .5O2(g) ----> H2O(I) H*= -286 Kj

which of the following is true,

A/ The reaction is exothermic

C/ The enthalpy of the products is less than that of the reactants.

D/ Heat is absorbed by the system

13/ Given the following reactions and H values,

2N2O(g) ----> O2(g) + 2N2(g) H = -164 KJ

2NH3(g) + 3N2O(g) ----> 4N2(g) + 3H2O(I) H = -1012 KJ

Calculation for H for 4NH3(g) + 3O2(g) -----> 2N2(g) + 6H2O(I)

delta H = 2 x -1012 + 3 x 164 = -1532 kJ

14/ what is the molality of a solution of 50 grams of propanol C3H8O in 152ml of water, If the density of water is 1g/ml

molality = moles/kg of solvent

= 50/60.10 x 0.152 = 5.47 molal

15/ 2.5 liters of aqueous solution containing 50 grams of Mgcl2 dissolved in pure water is prepared. The molarity of the solution is,

Molarity = moles/L

= 50/95.211 x 2.5 = 0.21 M

17/ A Cucumber is placed in a concentrated salt solution.

A/ Water will flow form the cucumber to the salt solution.

This is an Osmosis question. Osmosis is the travel of water from a high concentration of water to a low concentration of water.

Lots of salt in the salt solution therefore low water conc.
Lots of water in the cucumber therefore high water conc.

Therefore, water travels from cucumber to solution.

18/ When a water molecule forms a hydrogen bond with another water molecule, the Which atoms that are involved in the interaction are,

B/ A hydrogen form one molecule and an oxygen form the other molecule

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