Energy and Changes in Chemical Systems - Demo

The following is a sampling of questions from our Energy and Changes in Chemical Systems testbank.

Use the following line graph to answer questions # 3 - 4.

The higher line segment produced by the products results from
  1. an increase in the number of moles of reactants
  2. a decrease in the temperature of the reactants
  3. the condensation of the products
  4. the addition of energy
When 22.7 kg of table salt are compressed to the point that pressure and temperature cause the salt to liquefy and reform into a predetermined solid shape, the enthalpy change is ( fusion = 30.21 kJ/mol of NaCl)
  1. 11.7 MJ
  2. -11.7 MJ
  3. 686 kJ
  4. -686 kJ
Calculate the total energy change of 500 g of Al(l)solidifying from 950C to 23.0C. The molar enthalpy of solidification of aluminum is 10.67 kJ/mol. The specific heat capacity of Al(l) is 1.09 J/gC and Al(s) is 0.897 J/gC.
  1. 703 kJ
  2. 642 kJ
  3. 615 kJ
  4. 445 kJ
One of the components of acid rain is nitric acid. Nitric acid and nitrogen monoxide form when water vapor reacts with nitrogen dioxide gas. What is the heat of reaction for the formation of nitric acid?
  1. -400.2 kJ
  2. -292.5 kJ
  3. -115.8 kJ
  4. 97.0 kJ

Use the following information to answer question # 47.

The change in enthalpy for the combustion of propane in a furnace is
  1. -2043.9 kJ/mol
  2. -2251.5 kJ/mol
  3. -773.3 kJ/mol
  4. -980.9 kJ/mol
The potential energy diagram for the reaction between Ca(OH)2(s) and HCl(aq)

indicates an
  1. endothermic reaction with a = -196.7 kJ/mol
  2. endothermic reaction with a = 196.7 kJ/mol
  3. exothermic reaction with a = -196.7 kJ/mol
  4. exothermic reaction with a = 196.7 kJ/mol
Which experimental design forms the best comparison for heat production between two hydrocarbons?
  1. Measure out equal volumes of gasoline and grease. Ignite the samples. The sample that burns the longest has the higher molar enthalpy.
  2. Take 2 samples of fuel and ignite the fuels inside a bomb calorimeter. Record the highest temperature reached by the calorimeter water for each sample.
  3. Take a 1.00 mL sample of each of the fuels. Place the fuel sample in a bomb calorimeter and ignite. Record the highest temperature achieved. Repeat for the second sample.
  4. Use a graduated cylinder to measure out 1.00 mL samples of each of the fuels. Place the first sample into a styrofoam cup and ignite. Record the highest temperature reached. Repeat for the second sample.
In a reaction between Br2(l) and OH-(aq), the Br2(l) undergoes auto-oxidation-reduction or disproportionation which means
  1. the Br2(l) is both reduced and oxidized
  2. the Br2(l) is electrolyzed
  3. the Br2(l) is oxidized
  4. the Br2(l) is reduced
Which equation is not an example of a redox reaction?
  1. 6 CO2(g) + 6 H2O(l) ---> C6H12O6(s) + 6 O2(g)
  2. 2 Fe2O3(s) + 3 C(s) ---> 4 Fe(s) + 3 CO2(g)
  3. HCl(aq) + NaOH(aq) ---> H2O(l) + NaCl(aq)
  4. Cu(s) + Br2(l) ---> CuBr2(s)

Use the following information to answer questions # 36 - 37.

NR - no reaction
R - reaction

The strongest oxidizing agent is
  1. Fe2+(aq)
  2. Cl2(aq)
  3. Pb(s)
  4. Al(s)

Use the following information to answer questions # 40 - 44.

These results probably came from an experiment designed to
  1. display the factors involved in equilibrium reactions
  2. determine the reactivity of metallic anions
  3. show the effects of halogens on metals
  4. produce a simple redox table
The main reason MnO4-(aq) and Cr2O72-(aq) are commonly used in titrations is because they
  1. cause skin irritations
  2. provide a colour change
  3. give off very little energy
  4. do not take part in the reaction
If Na(s) was used as the standard electrode potential, the E value for Br2(l) would be
  1. - 3.78 V
  2. -1.64 V
  3. 1.07 V
  4. 3.78 V
Gil wished to silver plate his favourite baseball. He calculated that he needed 18.6 g of Ag(s). Using a 6.25 mol/L AgNO3(aq), how long would Gil have to run this cell at 1.25 A to electroplate his baseball?
  1. 0.924 h
  2. 1.24 h
  3. 1.85 h
  4. 3.70 h
Chlor-alkali electrolytic cells convert concentrated sodium chloride solutions into hydrogen gas and chlorine gas although oxygen gas should be produced. Why?
  1. The smaller oxide molecules have a harder time locating other oxide molecules to form oxygen.
  2. The reaction producing chlorine gas proceeds much faster than does the reaction to produce oxygen.
  3. Oxygen molecules are moving at such great speeds that they tend to collide and break up into oxide ions.
  4. The larger oxygen molecules are used to help in the liberation of the hydrogen gas produced at the cathode.
Increasing the pressure on the reaction:
2 N2O(g) ---> 2 N2(g) + O2(g)
would cause
  1. the reaction to reverse
  2. a temperature increase to occur
  3. a decrease in the size of the molecules
  4. the concentration of products to increase

If the Keq = 6.99 and the volume of bromochloride gas is 2.50 L at equilibrium, then the volume of chlorine gas is
  1. 1.12 L
  2. 1.05 L
  3. 0.894 L
  4. 0.946 L
For the reaction
2 NO2(g) + 2 H2O(l) ---> 2 HNO3(g) + H2(g)
the addition of a catalyst will
  1. produce less nitric acid
  2. reduce the activation energy
  3. lower the efficiency of the reaction
  4. increase the time required to cause a reaction
The pH of a 0.10 mol/L ethanoic acid solution is 3.65. The percent ionization of ethanoic acid is
  1. 37%
  2. 1.3%
  3. 0.37%
  4. 0.22%
Phenol red indicator is added to a 0.10 mol/L sample of hydrochloric acid. If 0.10 mol/L sodium hydroxide is added to the sample a student would note an equilibrium shift because the colour changes from
  1. red to yellow
  2. yellow to red
  3. green to yellow
  4. red to colourless

Use the following information to answer questions # 30 - 34.

How many protons can phosphoric acid donate?
  1. 4
  2. 3
  3. 2
  4. 1
150 mL of 2.50 mol/L hydrochloric acid and 150 mL of 2.50 mol/L magnesium hydroxide solutions are mixed. How many moles of magnesium hydroxide reacted?
  1. 0.188 mol
  2. 0.375 mol
  3. 0.750 mol
  4. 2.50 mol
The action of a buffer caused by the addition of an acid can be shown by the curvature of a line graph.

This buffering action is indicated by letter
  1. A
  2. B
  3. C
  4. D

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Last modified: April 14, 1999