CHM2030 Introduction to General, Organic, and Biological Chemistry
TEST EXAMPLES

(T) Activation energy can prevent reactions from taking place.
(F) When the volume of a gas is decreased by half, the pressure of the gas is doubled regardless of the change in temperature.
(F) When the temperature of a gas increases from 20 °C to 40 °C, the volume of the gas is doubled.
(F) When water evaporate to gaseous form at 100 °C, there is no heat needed since there is no change in temperature.
(T) The van der Waals forces are the weakest attractions between molecules.
(F) Only ionic compounds can be dissolved in water.
(F) Oxidation reactions are always determined by gaining oxygen(s).
(F) The activation energy for the forward reaction is always smaller than that of the reverse reaction.
(F) A reaction reaches equilibrium when the forward reaction and the reverse reaction occur at the same time.
(F) Once an equilibrium is reached, there is nothing going on.
(T) Water molecules attract each other through hydrogen bonds.
(F) That we can easily breath has nothing to do with water surface tension, because we are dealing with gas phase when breathing.
(T) Water and ethanol have the same vapor pressure at their boiling temperatures (100 °C and 78 °C, respectively).
(F) Solubilities of gases are proportional to temperature.
(T) Carbon dioxide bobbles form when a soda can is opened because the gas become less soluble when the pressure is released.
(F) The formula of water is H2O. Thus, water is formed by reacting 2 H with 1 O.
(T) A sucrose molecule C12H22O11 is 19 times heavier than a water molecule.
(F) One mole of nitrogen gas has 14 times less number of molecules as one mole of hydrogen gas.
(T) One mole is defined as the number of carbon atoms contained in 12.011 g carbon.
(T) When 5 moles of propane gas (C3H8) is burned, 15 moles of carbon dioxide is formed.
(T) Water can be formed by burning a compound that contains H.
(T) A reduction reaction is always accompanied by an oxidation reaction.
(T) Chemical reaction rate can be measured by the change in reactant concentration per unit of time.
(F) Increase in the temperature of a reaction can increase the rate of the reaction, which is due to decrease in the activation energy.
(F) Exothermic reactions can always occur because heat is given away and is not needed in the reactions.
(F) One atmosphere is the pressure to support any liquid to 760 mm height.
(T) Equal volumes of gases at the same temperature and pressure contain equal numbers of particles.
(T) Gas particles move at very high speeds.
(F) When a force is applied, the larger the contact area, the larger the pressure is on the area.
(T) Hurricanes are low pressure systems.
(F) Cold fronts from the north in the winter are low pressure systems.
(T) An idea gas has no volume at 0 K. There is no such thing in the real world.
(F) Water freezes at 0 °C. At that temperature water molecules stops moving.
(F) Standard temperature and pressure (STP) is defined as 300 K and 1 atm.
(T) Henry's law states that at a given temperature the solubility of a gas in a liquid is directly proportional to the pressure of the gas above the liquid.
(T) The hydrogen bond is a special kind of dipole-dipole interaction that involves a hydrogen atom.
(T) The London force is also a kind of dipole-dipole interaction, but just temporary.
(T) DNA double helix is "held together" by hydrogen bonds.
(T) Soaps can be easily made from fatty acids by reacting with sodium hydroxide.
(T) With enough energy, molecules can "escape" from both liquid phase and solid phase.
(F) At room temperature, dry ice "automatically" change into gaseous CO2. Thus, there is no energy needed at room temperature for this process.
(F) The boiling temperature of a liquid is strictly defined as the temperature when that particular liquid boils.
(F) Water cannot vaporize at near 0 °C because there is no enough kinetic energy for water molecule to "escape" from the liquid at that temperature.
(T) The vapor pressure of liquid A is higher than liquid B at room temperature. Therefore, you can expect that liquid A must have lower boiling temperature than liquid B.
(F) The boiling temperature of H2O is much higher than that of H2S. This is because there is no hydrogen bond at all between H2S molecules.
(F) The boiling temperature of CH4 is much lower than that of SiH4. This is because the hydrogen bond between SiH4 molecules is stronger than that in CH4.
(F) The relative humidity in a hot summer day in Florida is 95%. Therefore, the partial pressure of water vapor in that day is 760 mm Hg (or torr) ´ 0.95 = 722 mm Hg (or torr).
(T) The larger the hydrogen bonding interaction between molecules in a liquid, the higher the surface tension of the liquid is.
(F) Surface tension cannot be changed at all at STP.
(T) Glass has an amorphous structure.
(F) In the compound Ni(IO3)2, the number of molecules of O is 3 times more than that of Ni.
(F) Fact: The composition of calcium phosphate is 38.71% Ca, 20.00% P, and 41.29% O. Therefore: The molar ratio of Ca:P:O is 38.71:20.00:41.29 ~2:1:2
(T) Particles of all gases at the same temperature have the same average kinetic energy, regardless of the molar mass of the molecules.
(F) In chemistry, equilibrium is considered when there is no dynamic event going on.
(F) According to the Le Châtelierís principle, the equilibrium A + B h C + D can be easily disturbed by increasing the pressure.
(F) The volume of a gas is always proportional to temperature, regardless of the situation of the pressure of the gas.
(T) It is possible under certain conditions that the volume of a gas can increase even though the temperature decreases.
(T) If heat a supplied to the equilibrium 2SO2 + O2 h 2SO3 + heat, the reverse reaction is favored according to the Le Châtelierís principle.
(T) If heat a supplied to the equilibrium N2 + 6H2 h 2NH3 + heat, the reverse reaction is favored according to the Le Châtelierís principle.
(F) In an exothermic reaction heat should never be added to the system as it can shift the equilibrium to the reactants according to the Le Châtelierís principle. (What about ammonia production that we talked in the class?)
(T) Temperature can increase reaction rate by providing enough energy to overcome activation energy barrier.
(T) Enzymes do not provide any extra energy to a reaction, but simply lower the activation energy of the reaction.
Part II. Multiple Choice Questions

Here is the recipe for making pancakes that we discussed in one lecture:
            1 cup flour + 3 eggs + 2 cups milk = 9 pancakes
(2) 1. If you have 10 cups flour, 6 eggs and 2 cups of milk, how many pancakes can you prepare by following the recipe?
        (1) 18 (2) 9 (3) 90 (4) Cannot prepare any as the ingredients do not match the ratio on the recipe!
(1) 2. Which ingredient is left in the largest amount in terms of the number (not considering the units)?
        (1) flour (2) eggs (3) milk
(4) 3. How much of the above ingredient is left (not including the units)?
        (1) 2 (2) 3 (3) 5 (4) 9 (5) 8

In industrial preparation of ammonia, the reaction follows the following equation:
            3H2 + N2 ® 2NH3
    Answer the following 3 questions using this equation.
(3) 1. If you want to prepare 50 moles of NH3, how many moles of N2 is needed?
        (1) 100 (2) 50 (3) 25 (4) 31 (i.e., 50 ´ 17/28)
(4) 2. If you want to prepare 1 mole NH3, you need to have at least ____ g N2 and sufficient amount of H2.
        (1) 17 (2) 34 (3) 2 ´ (3/2) (4) 14 (5) 28
(2) 3. According to the Le Châtelierís principle, if pressure is applied to this reaction, the reaction favors
        (1) reactants (2) products (3) There in no influence!

(4) Which compound produces the largest amount of water when 1 mol of each is burned?
        (1) ethanol C2H5OH (2) ethane C2H6 (3) methyl ether C2H6O (4) Same amount!
(2) Which one of the following three compound needs the largest amount of oxygen to completely burn out if 1 mol of each is to be burned?
        (1) ethanol C2H5OH (2) ethane C2H6 (3) acetic acid CH3COOH (4) The same amount of oxygen is needed.
(2) When 1 mole of the compound C3H8O3 is completely burned, how many moles of water is formed?
        (1) 3 (2) 4 (3) 6 (4) 8

Use the following equation to answer questions 1-3.
            2Al(OH)3 + 3H2SO4 ® Al2(SO4)3 + 6H2O
(4) 1. How many moles of Al(OH)3 are required to completely react with 1.5 mol of H2SO4?
        (1) 3.0 (2) 1.5 (3) 2.0 (4) 1.0
(3) 2. How many moles of water is formed when 78 g Al(OH)3 is reacted with sufficient amount of sulfuric acid?
        (1) 1 (2) 2 (3) 3 (4) 6
(3) 3. The minimum amount of sulfuric acid to completely react with 1 mol Al(OH)3 is ____ g.
        (1) 49 (2) 98 (3) 147 (4) 196 (5) 294

The equilibrium constant Keq for the question
            A + 5B h 3C + 4D + heat
    is expressed as [C]3 [D]4/[A] [B]5        Note: [heat] is not in the equation!

(5) The activation energy of a reaction
        (1) is not affected by a catalyst.  (2) is always higher in an endothermic reaction than in an exothermic reaction.
        (3) is always the same for a forward and a reverse reaction. (4) is changed by changing the temperature.
        (5) All the above are not correct!

(5) Redox reactions can be determined by
        (1) loss of electron(s)   (2) gaining electron(s)   (3) gaining oxygen(s)
        (4) gaining hydrogen   (5) All the above can serve as criteria.

(3) If the equilibrium constant for the equilibrium A h 2B is 9, the concentration of B is ___ times than that of A at equilibrium.
        (1) 1/9 (2) 1 (3) 3 (4) 9/2 (5) 9

(4) The equilibrium Keq of a reaction is 4 x 107. At equilibrium,
        (1) the reactants are favored.  (2) the reactants and products are present in equal amount in terms of moles.
        (3) the rate of the forward reaction is much greater than the rate of the reverse reaction.
        (4) the products are favored.   (5) Cannot be determined without knowing what the reaction is.

(1) When pressure is applied to the equilibrium "N2 + 3H2 h 2NH3 + heat", the reaction shifts to
        (1) right. (2) left (3) nothing change (4) cannot predict.

(2) When heat is applied to the equilibrium "N2 + 3H2 h 2NH3 + heat", the reaction shifts to
        (1) right. (2) left (3) nothing change (4) cannot predict.

(3) When 1.00 g water is completely changed into gaseous form at STP (assuming gaseous water follows the idea gas law), its volume is
        (1) 1.00 L (2) 18.0 L (3) 1.25 L (4) cannot be obtained!

(3) A container with a volume 22.4 L contains 1.0 mol nitrogen and 2.0 mol hydrogen at 0 °C. Which of the following statement is true? (The molar volume of gases is 22.4 L.)
        (1) The pressure in the container is 1.0 atm.  (2) The partial pressures of N2 and H2 are the same.
        (3) The pressure in the container is 2280 mm Hg.  (4) The partial pressure of N2 is 1.0/3.0 atm.

(2) A gas sample occupies 225 mL at 765 mm Hg. What volume does the gas occupy at 475 mm Hg?
        (1) 140 mL (2) 362 mL (3) 1.60 x 103 mL (4) 7.16 x 10Ė3 mL

(4) Which of the following changes would not cause an increase in the pressure of a gaseous system?
        (1) Additional amount of the same gas is added to the container.
        (2) A different gas is added to the container.  (3) The temperature is increased.
        (4) The volume of the container is made larger.

(3) Molar volume of gas is 22.4 L at STP. What is the volume of 1.0 g methanol (CH3OH) when it is completely changed into gaseous form?
        (1) 22.4 L (2) 0.045 L (3) 0.7 L (4) 1.4 L

The relationship between pressure (P) and volume (V) at constant temperature is:
         P1/P2 = V2/V1;  P x V is always a constant.

(3) The pressure on 3.60 L of an anesthetic gas is changed from 780 to 376 mm Hg. What is the new volume if the temperature remains constant?
        (1) 1.74 L (2) 3.60 L (3) 7.47 L (4) cannot determine

(2) The relationship between temperature (T) and volume (V) at constant pressure is:
        (1) V1 ´ T1 = V2 ´ T2  (2) V1/T1 = V2/T2

(3) An inflated balloon at 20.0 °C has a volume 2.0 L. What is the new volume when it is heated to 40.0 °C?
        (1) 4.0 L (2) 1.0 L (3) 2.1 L (4) 1.9 L

Which is a false statement about the ideal gas law?
        This law also can be perfectly applied to vapors of liquids.  (Because vapor can be liquified.)

(1) How much methane is in 2.24 L at 15.0 atm and 42 °C, asumming it follow the idea gas law? The gas constant is 0.082 atm L/mol K.
        (1) 20.8 g (2) 41.6 g (3) 9.76 mol (4) 0.1 mol

(4) After one minutes, a reactant in a reaction changes from 10 mol to 7 mol. What is the average reaction rate of this reaction?
        (1) 0.17 mol/sec (2) 0.12 mol/sec (3) 0.28 mol/sec (4) 0.05 mol/sec

(2) In a chemical reaction,
        (1) products always have lower energy.    (2) the reaction rate is controlled by the activation energy.
        (3) forward and back reactions have the same activation energy.
        (4) Catalysts accelerate only the forward reaction rate, but not the back reaction rate.

(5) In the reaction A ® B, the rate of appearance of B is 0.05 mol/min,
        (1) the disappearance of A is also 0.05 mol/min.
        (2) the appearance of B can be changed by changing temperature.
        (3) the appearance of B is 3 mol/hour.
        (4) All of the above are wrong!
        (5) All of the above are correct!

(3) In the reaction A ® 2B, the rate of appearance of B is 2.0 mol/min,
        (1) the disappearance of A is also 2.0 mol/min.
        (2) the disappearance of A is faster than the appearance of B.
        (3) the disappearance of A is slower than the appearance of B.

(4) In the reaction 3O2 ® 2O3 (ozone), the rate of appearance of ozone is 1.50 mol/min under certain conditions. What is the rate of disappearance of oxygen?
        (1) 1.50 mol/min (2) 3.00 mol/min (3) 4.50 mol/min (4) 2.25 mol/min

(1) In the above reaction, the rate of disappearance of oxygen becomes 1.50 mol/min under some different conditions. What is the rate of appearance of ozone now?
        (1) 1.00 mol/min (2) 1.50 mol/min (3) 2.00 mol/min (4) 2.25 mol/min

(1) The activation energy of two different reaction are (A) 24 kJ and (B) 53 kJ, respectively. If the temperatures of both reactions are identical, which has higher reaction rate?
        (1) A (2) B

(3) When one mole of glucose (C6H12O6) is oxidized in our body, about 680 kcal heat is released. When 18 g glucose is oxidized, how much heat is released?
        (1) 38 kcal (2) 680 kcal (3) 68 kcal (4) None of above!

(4) In the reaction A + B ® 2C + 10 cal, the equilibrium concentrations are found to be [A] = [B] = 0.5 M, and [C] = 0.1 M. What is the equilibrium of this reaction?
        (1) 25 (2) 2.5 (3) 0.4 (4) 0.04

Given the equilibrium reaction,
            131 kJ + C(s) + H2O(g) h CO(g) + H2(g); s: solid and g: gas
    (This is the famous water-gas shift reaction that produces the useful "fuel gas" H2.)
NOTE:  Don't consider heat and solid for the calculation of an equilibrium constant.

complete the following questions 1-5.
(2) 1. Increase in temperature, the equilibrium is moved to
        (1) left (2) right (3) No effect!
(2) 2. Increase in water vapor concentration, the equilibrium is moved to
        (1) left (2) right (3) No effect!
(1) 3. Adding CO, the equilibrium is moved to
        (1) left (2) right (3) No effect!
(1) 4. Increase in pressure, the equilibrium is moved to
        (1) left (2) right (3) No effect!
(3) 5. Adding a catalyst, the equilibrium is moved to
        (1) left (2) right (3) No effect!

(4) Which is the most important secondary force for non-polar molecules?
        (1) hydrogen bond   (2) dipole-dipole interaction   (3) non-polar interaction  (4) London force

(1) Which is the most important secondary force in biomolecules?
        (1) hydrogen bond   (2) dipole-dipole interaction   (3) non-polar interaction  (4) London force

(1) The two helices in DNA double helix are held by
        (1) hydrogen bond (2) dipole-dipole interaction (3) non-polar interaction
        (4) London force (5) covalent bond

(1) The surface tension of water is very high, which is due to attraction of water molecules by
        (1) hydrogen bond (2) dipole-dipole interaction (3) non-polar interaction
        (4) London force (5) covalent bond

(4) The boiling temperature of methane is not extreme low near the absolute zero. This is due to the interaction between methane molecules via
        (1) hydrogen bond (2) dipole-dipole interaction (3) non-polar interaction
        (4) London force (5) covalent bond

(4) Which compound/substance can be dissolved in both water and oil?
        (1) sugar (2) table salt (3) syrup (4) soap

(2) The equilibrium vapor pressure of water is 23.8 torr at 25 °C. If the relative humidity is 75%, the partial pressure of atmospheric water is ____ torr.
        (1) 1785 (2) 17.85 (3) 0.32 (4) 31.6