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Version "Exam"

1. Which of the following sets of properties describes a typical ionic compound:

(a)    molecule, low melting point, electron sharing

(b)    high melting point, good conductor, high water solubility

(c)    gas, low solubility in water, poor conductor

(d)    liquid, good conductor, low solubility in water

 

2. Which element when combined with fluorine would most likely form an ionic compound

(a)    lithium

(b)    carbon

(c)    phosphorus

(d)    chlorine

 

3. Which of the following accounts for an ionic bond?

(a)    oppositely-charged ions attract

(b)    two atoms share two electrons

(c)    two atoms share more than two electrons

(d)    like-charged ions attract

 

4. Which of the following compounds would not have covalent bonds

(a)    NO2

(b)    Cs2O

(c)    N2O

(d)    H2O2

 

5. The formula of potassium sulfate is:

(a)    K2(SO4)2

(b)    KSO4

(c)    K2S

(d)    K2SO4

 

6. The formula for sodium sulfide is:

(a)    NaS2

(b)    NaS

(c)    Na3S2

(d)    Na2S

 

7. Molecular compounds:

(a)    usually have high melting points (greater than 300oC)

(b)    are formed by the sharing of electrons between atoms

(c)    are usually solids at room temperature

(d)    none of these

 

8. A single covalent bond is

(a)    when electrons are transferred from one atom to another

(b)    between metals and nonmetals

(c)    when atoms share electrons

(d)    when an element becomes a noble gas

 

 

9. A molecule of carbon monoxide has a (drawing a dot structure might help answer this question)

(a)    single covalent bond

(b)    double covalent bond

(c)    triple covalent bond

(d)    tetra covalent bond

 

10. The polarity of the H-F bond in hydrogen fluoride is due to:

(a)    the high electronegativity value of H

(b)    fluorine’s low electronegativity value

(c)    the net positive charge of the molecule

(d)    the electronegativity difference between H and F

 

11. The mass of one mole of phosphorus pentoxide, P2O5 is

(a)    70.0 g

(b)    92.0 g

(c)    110.0 g

(d)    142.0 g

 

12. How many moles is 14 g of calcium carbonate, CaCO3?

(a)    0.72 mol

(b)    0.14 mol

(c)    1.4 mol

(d)    7.2 mol

 

13. How many moles of O2 are produced for each 1.0 mol of Al produced?

 2 Al2O3(s) --> 4Al(s) + 3O2(g)

      (a)    1.3

(b)    3.0

(c)    12

(d)    0.75

 

14. Calculate the number of moles of NH3 produced when 5.4 g of hydrogen reacts with nitrogen.  The balanced equation is:

 

N2(g) + 3H2(g) --> 2NH3 (g)

 

(a)    3.6 mol NH3

(b)    1.8 mol NH3

(c)    5.4 mol NH3

(d)    0.90 mol NH3

 

15. In which of these systems is entropy (disorder) decreasing

(a)    air escaping from a tire

(b)    melting snow

(c)    dissolving salt in water

(d)    cooling a liquid

 

16. Which of the following changes will cause the equilibrium position to move to the left?

 

4NH3(g) + 3O2(g)  2N2(g) + 6H2O(g) + heat

 

(a)    adding more O2

(b)    heating the reaction

(c)    removing H2O

(d)    adding a catalyst

 

17. A chemical reaction always occurs if:

(a)    it is endothermic and there is an entropy increase

(b)    it is endothermic and there is an entropy decease

(c)    it is exothermic and there is an entropy increase

(d)    it is exothermic and there is an entropy decrease

 

18. What two factors would be expected to decrease the rate of a chemical reaction?

(a)    decrease in temperature, use of a catalyst

(b)    decrease in particle size, increase in surface area

(c)    decrease in temperature, decrease in reactant concentration

(d)    decrease in particle size, use of a catalyst

 

19. The activation barrier:

(a)    is lowered by the presence of a catalyst

(b)    can be lowered by increasing the concentration of reactants

(c)    can be lowered by increasing the temperature of the reaction

(d)    is negligible for an endothermic reaction

 

20. A large equilibrium constant indicates

(a)    that products are favored at equilibrium

(b)    that the reaction is very fast

(c)    that the reaction is very slow

(d)    that a catalyst is necessary for the reaction to occur

21.

(a) Draw the Lewis dot structure for a single atom of hydrogen and for a single atom of nitrogen

  

(b) Draw the Lewis dot structure for the ammonia molecule NH3

 

 (c) Describe the shape of the NH3 molecule and explain why it takes on this shape.

 

(d) Is the NH3 molecule polar?  Explain why or why not.

 

 22. Balance the following chemical reaction:

 

C2H5OH   +   O2  -->   CO2    +   H2O