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Chemistry 105A Exam I - October 2009, Exams of Chemistry

Albright College Chemistry

The questions and answers for exam i of chemistry 105a, held on october 2, 2009. The exam covers various topics in chemistry such as atomic structure, balancing chemical equations, molarity, and redox reactions.

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Pre 2010

Uploaded on 12/04/2009

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Chemistry 105A Exam I October 2, 2009

I certify I have not used a programming calculator for anything other than simple

mathematical operations.

_______________________________________ (Signature)

_______________________________________ (Printed name)

Multiple choice (20 questions, 3 pts. each) Darken the correct answer on the answer

sheet. Remember there are also 3 problems given after the multiple-choice

questions. Budget your time accordingly.

1. A homogeneous substance that has variable composition and can be separated

by physical means describes which of the following substances?

a) solution

b) pure substance

c) element

d) compound

2. Which one of the following is a physical process?

a) the formation of polyethylene from ethylene

b) the rusting of iron

c) the baking of a potato

d) the condensation of water vapor

e) the explosion of nitroglycerine

3. How many significant figures should there be in the answer to the following

problem?

a) 1 b) 2 c) 3 d) 4

4. 20.0 cubic yards is how many cubic meters? (1m = 1.0936 yd)

a) 6.02 m3b) 15.3 m3c) 2.37 m3d) 0.425 m3e) 98.6 m3

5. Alcohol has a density of 0.78 g/ml. What is the volume of a shot glass that holds

69 g of alcohol? (128 oz = 3.7854 L)

a) 1.6 oz. b) 1.8 oz. c) 2 oz. d) 3 oz.

CHE 105A – Fall 2009 –Exam I WHITE 1 / 4

47.17

)76.1189.15( 

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Chemistry 105A Exam I October 2, 2009 I certify I have not used a programming calculator for anything other than simple mathematical operations. _______________________________________ (Signature) _______________________________________ (Printed name) Multiple choice (20 questions, 3 pts. each) Darken the correct answer on the answer sheet. Remember there are also 3 problems given after the multiple-choice questions. Budget your time accordingly.

A homogeneous substance that has variable composition and can be separated by physical means describes which of the following substances? a) solution b) pure substance c) element d) compound
Which one of the following is a physical process? a) the formation of polyethylene from ethylene b) the rusting of iron c) the baking of a potato d) the condensation of water vapor e) the explosion of nitroglycerine
How many significant figures should there be in the answer to the following problem? a) 1 b) 2 c) 3 d) 4
20.0 cubic yards is how many cubic meters? (1m = 1.0936 yd) a) 6.02 m^3 b) 15.3 m^3 c) 2.37 m^3 d) 0.425 m^3 e) 98.6 m^3
Alcohol has a density of 0.78 g/ml. What is the volume of a shot glass that holds 69 g of alcohol? (128 oz = 3.7854 L) a) 1.6 oz. b) 1.8 oz. c) 2 oz. d) 3 oz. 17. 47 ( 15. 89  11. 76 )

Which of the following molecular formulas is also an empirical formula? a ) C (^) 1 2 H (^) 1 4 O 6 b ) H 2 O (^2) c ) C 2 H 6 S O d) C 6 H 6 O 3 e ) H 2 P 4 O 6
Use the following information to identify the atom or ion. Mass number Protons Neutrons Electrons 56 25 31 21 a ) M n 4 +^ b ) B a 2 +^ c ) S c d ) M n
Which element has a variable oxidation state? a) Ba b) Al c) Ca d) Sr e) Cr
Sulfide ion is a) S O 2 3 2 ^ b) (^) S^2 ^ c) SO^23 ^ d) (^) SO^24 ^ e) (^) HSO 4 
What is the coefficient on H 2 O when the equation below is properly completed and balanced? C s ( s ) + H 2 O ( l )  a) 2 b) 4 c) 1 d) 3 e) 6
The mass percentage of S in C H O SN 13 11 5 3 is a) 48.59% b) 3.45 % c) 13.09 % d) 9.99 % e) 24.90 %
What are the respective molar concentrations of Fe3+^ and I -^ produced by dissolving 0.200 mole of FeI 3 in water to produce 725 ml of solution? a) 0.276 M and 0.276 M b) 0.145 M and 0.0483 M c) 0.276 M and 0.828 M d) 0.828 M and 0.276 M e) 0.145 M and 0.435 M
A compound containing potassium, chlorine, and oxygen was found to be 36.6% by weight potassium, 33.3% chlorine, and 30.0% oxygen. What is the empirical formula of the compound? a ) K C l O 3 b ) K C l O 4 c ) K C l O 2 d ) K C lO
How many molecules are present in a 500 mg tablet of vitamin C, C 6 H 8 O 6?

TO RECEIVE FULL CREDIT, YOU MUST SHOW YOUR WORK ON THE ANSWER

SHEET FOR THE FOLLOWING PROBLEMS!

(10 pts.) Explain Rutherford's experiment and what conclusions he made about atomic structure based upon the results.
(12 pts.) A 25.0 mL sample of NaOH was neutralized by 28.2 mL of a 0.355 M H 2 SO 4 solution. a) Provide the balanced chemical equation for this process. b) Based on the data, determine the molarity of the sodium hydroxide solution.
(18 pts.) In an oxidation-reduction reaction, 7.69 kg of solid Fe 3 O 4 (s) is reacted with carbon monoxide to produce iron and CO 2 according to the reaction below. a) How much CO(g) is needed to react with the given amount of Fe 3 O 4? b) What is the theoretical yield of Fe(s) in this reaction? c) Given an actual yield of 4. kg of Fe(s), determine the percent yield of the reaction. Fe 3 O 4 (s) + 4CO(g)  3Fe(s) + 4CO 2 (g)

ANSWER KEY

Chemistry 105 Exam I October 2, 2009

a 2. d
1. c 4. b
d 6. c
a 8. e
b 10. a
d 12. c
c 14. a
a 16. b
b 18. c
d 20. c

21. Rutherford bombarded gold foil with positively charged,  particles  

4 2 He nuclei and detected the trajectory of the particles that went through using photographic film arranged in a circular configuration around the source of  particles. Rutherford and his graduate students discovered that while some particles went through the foil without deflection; others had their path bent by an apparent collision within the foil. Rutherford concluded that atoms consist of heavier particles, protons and neutrons, concentrated in a positively charged nucleus surrounded by a much larger, low-density region of the electron cloud which is mostly empty space (Figure 2.12, p. 44 Brown et al. (2009). Additionally, he concluded the nucleus had a positive charge that repels positively charge particles such as  particles and, along with the mass of the nucleus, deflects them at large angles while the diffuse, negatively charged electron cloud allows the positively charged, a particles to go through without deflection. Rutherford’s work led to the nuclear model of the atom that is know today and refuted the idea of a plum-pudding arrangement of sub-atomic particles put forth by J.J. Thomson which should have produced small or no deflection.