CHEM 1364

Test 2

Fall 1997

SHORT ANSWER: 2 points each. Fill in the blank with the most correct answer.

1. The ___________________ coefficient for a balanced chemical equation tells the number of molecules produced or consumed during the reaction.

2. The _______________ yield for a reaction is the amount of material we should produce if everything works perfectly.

3. The _________________ reactant is the reactant that is consumed completely in a chemical reaction.

4. A(n) ___________________ is formed when two ions (which together form an insoluble compound) are mixed.

5. The ____________ ionic equation shows only the ions involved in a chemical process.

6. A(n) ______________ acid donates some, but not all, of it's hydrogen ions to water to form hydronium ions (H3O+).

7. _________________ is the process of adding an accurately-measured volume of reactant to a substance in order to determine the amount of an unknown.

8. The term ___________ reaction is used to describe a process for which one species donates electrons to another.

9. A(n) _______________ displacement reaction occurs when a species in it's elemental form is oxidized, causing an oxidized species to be reduced to it's elemental form.

10. ________________ Law describes the relationship between pressure and volume for an gas.

11. _________________ Zero is the lowest temperature possible, and was discovered by Lord Kelvin during his investigation of the relationship between volume and temperature for a gas.

12. A(n) ____________ gas is one that has molecular volume equal to zero, and the intermolecular attractive forces are also equal to zero.

13. The ________________ pressure of a gas in a mixture is equal to the pressure the pure gas would exhibit under the same volume/temperature conditions.

14. The _________________ equation is an attempt to compensate for the deviations from ideal behavior that 'real' gases exhibit.

15. The _____________________________ Theory consists of five postulates that help us to understand at a microscopic level the changes we observe at a macroscopic level.

PROBLEMS (Point totals are shown in parenthesis). Show your work and circle your answers where appropriate for full credit.

16. (15) For each of the following process predict if a reaction will occur. If a reaction does occur write the formula for the products and write the balanced molecular equation. If a reaction does not occur, write N/R to indicate that no reaction occurs:

a) KCl + AgNO3

b) Ag + ZnSO4

c) Na2SO4 + Pb(ClO4)2

d) NaC2H3O2 + (NH4)3PO4

e) Mg + FeCl2

17. (15) For the above reactions that occur, write the net ionic equation.

18. (15) Phosphorous(V) chloride reacts with water as follows:

PCl5(s) + 4H2O(l) H3PO4(l) + 5HCl(g)

How many grams of H3PO4 (MW = 208.2) can be produced from 20.0 g of PCl5 and 5.00 g of water.

19. (10) What volume of HCl gas is produced by the above reaction at 25C and 100.0 kPa?

20. (15) A gas is analyzed to determine it's molecular weight. 4.10 g of the gas was found to have a pressure of 543 torr when the volume was 1.00 L and the temperature was 37C. What is the molecular weight of the gas?

EXTRA CREDIT (10) The pitch of the human voice depends on a number of factors, one of which is the density of the gas passing by the vocal cords, with lower the density gases increasing the pitch (I'm sure we've all heard the 'Donald Duck' voice when we breathe helium). Would the gas in Problem #20 cause an increase or a decrease in the pitch of a human voice? Explain.

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