February 2017

Avogadro Exam 1988: Part 2

Jean Hein

To celebrate the 30th year of the Avogadro Exam we are reprinting questions from the first exam in 1988 in this and upcoming issues. The exam was, and is, aimed at grade 11 chemistry students. Consider registering your students to write the 2017 Avogadro Exam https://uwaterloo.ca/chemistry/exams in May 2017.

  1. Which of the following substances have melting points above 500 °C? (1) copper ,  (2) sodium chloride,  (3)  bromine, and (4) propane.
    1.  (1) and (2) only   
    2.  (1) and (3) only 
    3.  (1) and (4) only
    4.  (2) and (3) only
    5.  (3) and (4) only
  1. What charge does the ion BF4n have?
    1. n = 3-  
    2. n = 2- 
    3. n = 1-
    4. n = 1+
    5. n = 2+             
  2. What volume of hydrogen will have nearly the same number of molecules as 1.00 L of oxygen gas, if both are measured at the same temperature and pressure?
    1. 22.4 L hydrogen 
    2. 16.0 L hydrogen
    3. 2.00 L hydrogen
    4. 1.00 L hydrogen
    5. 0.500 L hydrogen
  3. What is the relative molar mass of an ideal gas if, at 100 °C and 50.0 kPa, a 500 mL sample has a mass of 0.322 g? The Ideal Gas Constant is 8.314 J K-1 mol-1.
    1. 159.8     
    2. 39.9
    3. 29.2
    4. 25.1
    5. 16.4    
  4. Select the one incorrect statement about ideal gases:
    1. Dalton’s Law of Partial Pressures states that the total pressure of a mixture of non-reacting gases is equal to the sum of the partial pressures of all the gases in the mixture.
    2. Gay-Lussac’s Law of Combining Volumes for reacting gases says that the volumes of gases used or produced in a chemical reaction, and measured at the same temperature and pressure, can be expressed as the ratios of small, whole numbers.
    3. Avogadro’s Principle claims that equal volumes of two gases contain the same number of molecules, provided the pressure and temperature are the same.
    4. According to Charles’ Law, a plot of V against T extrapolated to V=0 for a gas will cross the T-axis at absolute zero.
    5. Boyle’s Law predicts that a plot of V against P will pass through the point P=0, V=0.
  5. For which gas (all at the same temperature) will the average speed of the molecules be the highest?
    1. Ar     
    2. O2 
    3. CO2
    4. Cl2
    5. CH4       
  6. The reaction of calcium carbonate with dilute aqueous hydrochloric acid produces
    1. H2(g) and Ca(OH)2(s)
    2. CaC2(s) and Cl2(g) 
    3. CO2(g) and CaCl2(aq)
    4. Cl2(g) and CaO(s)
    5. CaO(s) and CO2(g)
  7. What is “x” when the following equation is balanced with “1” as the NH3 coefficient? 1 NH3(g)  +  x O2(g)  -->  y NO(g)  +  z H2O(g)
    1. 5/4    
    2. 5/3
    3. 5/2
    4. 1
    5. 5         
  8. If the following equation is obeyed, how many moles of ammonia are needed to produce 801 mol of hydrogen, H2? 2 NH3(g) --> N2(g)  +  3 H2(g)
    1. 1203 mol  
    2. 534 mol 
    3. 267 mol
    4. 22.4 mol
    5.  2 mol     
  9. What is the main gaseous product of the reaction of hot, aqueous hydrochloric acid with solid manganese(IV) oxide?
    1. Mn2O7(g)    
    2. MnCl2(g)  
    3. ClO2(g)
    4. Cl2(g)
    5.  MnCl4(g)       

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