Final Exam, Che 101, Summer 2007 (200 Pts)

Name ______NSCC, Summer 2007

FINAL EXAM, CHE 101, SUMMER 2007 (200 PTS)

Part A. Chapters 1 - 4, and 9 1. Classify each of the following elements as a metal, nonmetal, or metalloid

Carbon Chromium Silicon

a. Nonmetal Metalloid Metal b. Metalloid Metal Nonmetal c. Metal Nonmetal Metalloid d. Nonmetal Metal Metalloid e. Metalloid Metal Metalloid

2. In one of your laboratory experiments you used the concept of water displacement to figure out the mass of an object. If you placed a ceramic object, with a density of 2.084 g/mL, in a graduated cylinder containing 60.0 mL of water and the water level rose to 92.6 mL, what is the mass of the object? a. 15.6 g b. 44.4 g c. 67.9 g d. 3.22 g e. 73.2 g

3. What is the mass number of an ion with 29 protons, 36 neutrons, and 27 electrons? a. 65 b. 36 c. 56 d. 92 e. 29

4. What is the electron configuration of vanadium (V, atomic number 23) a. 1s22s22p63s23p64s23d5 b. [Ne] 4s33d3 c. [Ar] 4s23d3 d. [Ar] 4s03d5 e. [Ne] 4s03d5

5. What is the product of -emission in the following reaction? 126 0  + 50 Sn ? -1e

126 126 126 126 a. 51Sn b. 50Sn c. 49In d. 51Sb

1 Name ______NSCC, Summer 2007

Problem Solving: Chapters 1 – 4, and 9

-7 6. Assume that at certain temperature, the equilibrium constant (Kc) equals 5.8 x 10 for the following balanced reaction

O2 (g) + O (g)  O3 (g)

2 How many grams of O3 (g) were produced if the initial concentration of both reactants was 1 x 10 M and the final volume of the reaction is 1.0 L? [Hint, figure out moles of product first].

7. As we learned in class, in covalent compounds atoms tend to share electrons, which form covalent bonds, in order to achieve an octet. We used electron dot formulas to illustrate which valence electrons are shared and which are lone pairs. a. Below is the structure of acetyl chloride, drawn with bonds and electron dots. Determine how many bonding electrons and lone pairs are shown.

# of bonding electrons: ______# of lone pairs: ______

b. Write the formula for sulfur dioxide and show its electron dot structure

Formula:

Electron dot structure:

Part B. Chapters 5, 6, and 8

8. How many grams are there in 0.500 moles of sodium chloride? a. 14.61 g b. 7.306 g c. 29.23 g d. 58.46 g e. 0.500 g

9. How many moles of oxygen will form when 5.0 moles of lead oxide react (reaction is shown below)?

2 PbO(s) → 2 Pb(s) + O2(g) a. 5.00 moles b. 2.50 moles c. 10.0 moles d. 80.0 moles e. 54.5 moles

10. The heat of fusion for water is 80 cal/g, heat of vaporization is 540 cal/g, and specific heat is 1cal/g oC. How many calories are required to convert 25.5 g of ice at oC to steam at 100 oC?

a. 18360 calories b. 91800 calories c. 16320 calories d. 2550 calories e. 15810 calories

11. What is the molarity of a solution containing 60.0 grams of KCl in 0.500 L of solution? a. 120.0 M b. 0.00833 M c. 1.61 M d. 0.621 M e. 34.5 M

12. Barium phosphate is formed from the reaction of barium chloride and sodium phosphate as shown in the balanced equation below. What mass of barium phosphate is produced by the reaction of 200.0 mL of 0.1200 M solution of barium chloride with excess sodium phosphate?

3BaCl2 + 2Na3PO4  Ba3(PO4)2 + 6NaCl

a. 0.004 g b. 14.42 g c. 4.808 g d. 0.234 g e. 5.345 g

Problem Solving: Chapters 5, 6, and 8

13. Aspartame is an artificial sweetener that is 160 times sweeter than sucrose (table sugar) when dissolved in water. It is marketed as Nutra-Sweet. The molecular formula of aspartame is C14H18N2O5 a. Calculate the molar mass of aspartame

b. How many moles are in 10.0 g aspartame?

c. How many molecules are in 5.0 g aspartame?

14. Nitrogen gas can be prepared by passing gaseous ammonia (NH3) over solid copper (II) oxide at high temperatures. The other products of the reaction, in addition to nitrogen gas, are solid copper and water vapor, H2O(g). A sample containing 18.1 g of NH3 is reacted with 90.4 g of CuO to give the above products. a. Write balanced equation for this reaction (note all the formulas are given above).

b. Which is the limiting reactant, NH3 or CuO?

c. How many grams of N2 will be formed?

Part C. Chapters 7 and 10 + -4 15. What is the pH of a solution with [H3O ] = 1.0 x 10 a. –4.00 b. 2.50 c. 4.00 d. 1.0 x 10-2 e. – 2.50

- 16. What is the concentration of [OH ] in a solution with pH of 4.5 a. 3.16 x 10–5 b. 4.50 c. 3.16 x 10–10 d. 1.00 x 10–14 e. 7.00

17. How many milliliters of 0.30 M NaOH are required to completely neutralize 25.0 mL of 0.40 M HCl? a. 25.0 mL b. 18.8 mL c. 33.3 mL d. 4.80 mL e. 12.5 mL

18. A small balloon has a volume of 0.50 L at a temperature of 10 °C. What is the new volume of the balloon when the temperature rises to 25 °C and the pressure remains constant? a. 0.53 L b. 0.47 L c. 1.3 L d. 1.0 L e. 2.0 L

19. What is the molar mass of a piece of metal with a mass of 8.50 g if it has a volume of 2.0 L at 25 oC and pressure of 1.0 atm? [R = 0.0821 atm.L/mol.K] a. 0.0817 g/mole b. 103.98 g/mole c. 0.0096 g/mole d. 0.9744 g/mole e. 8.7231 g/mole

Problem Solving: Chapters 7 and 10

20. We learned the concept of acid strength. We said that acids are classified as strong or weak. Strong acids dissociate nearly completely in water whereas weak acids dissociate only slightly. We said that the acid dissociation constant, Ka, is a measure of acid strength for weak acids [Recall there are six strong acids]. Lets apply this concept to proteins.

Proteins are complex biological molecules made of smaller molecules called amino acids. Five common amino acids and their Ka values are listed below. Rank them from strongest to weakest acid.

Amino Acid glutamine 6×10−3 arginine 2×10−2 threonine 3×10−3 tryptophan 4×10−3 proline 1×10−2

[If it helps you, convert the scientific notation to standard format, for instance 1 x 10–2 = 0.01]

Strongest: ______Weakest

Extra Credit (10 pts)

21. A volume of 18.0 L contains a mixture of 0.250 moles N2, 0.25 moles O2, and an unknown quantity of He. The temperature of the mixture is 0 oC, and the total pressure is 1.00 atm. How many grams of helium are present in the gas mixture? [Hint, use the ideal gas law to figure out the total moles of the gas, and work your way from there on].