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Chem 1 Midterm Question and Solutions, Exams of Chemistry

Chem 1800 Midterm 1 solutions. It has questions and answers

Typology: Exams

2017/2018

Uploaded on 03/15/2018

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CHEM1800U Winter 2014
Midterm Test 1 January 30/31, 2014
CRN 70066 70067 72840
Name __________ ____ _____ _____ _____ ____ _____ __
Student Number __________ ____ _____ _____ _____ ____ _____ __
Time allowed = 75 minutes
1. Read each part of each problem carefully and thoroughly.
2. You must show each step in a calculation clearly and indicate all values, including
physical constants used to obtain your result.
3. Report all answers to the correct number of significant figures and with units
where applicable. Please indicate your final answer clearly.
4. If you don’t understand what the problem is requesting, raise your hand and a
proctor will come to your desk.
5. Data / tables / a periodic table are given on the last page. You may detach this
page once the exam has started.
6. You may use a non-programmable, scientific calculator. No other electronic
devices or other aids are permitted.
7. ANSWER IN THE SPACE PROVIDED
At the end of the test, submit the entire examination.
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CHEM1800U Winter 2014

Midterm Test 1 January 30/31, 2014

CRN 70066 70067 72840

Name ________________________________________

Student Number ________________________________________

Time allowed = 75 minutes

1. Read each part of each problem carefully and thoroughly.

2. You must show each step in a calculation clearly and indicate all values, including

physical constants used to obtain your result.

3. Report all answers to the correct number of significant figures and with units

where applicable. Please indicate your final answer clearly.

4. If you don’t understand what the problem is requesting, raise your hand and a

proctor will come to your desk.

5. Data / tables / a periodic table are given on the last page. You may detach this

page once the exam has started.

6. You may use a non-programmable, scientific calculator. No other electronic

devices or other aids are permitted.

7. ANSWER IN THE SPACE PROVIDED

At the end of the test, submit the entire examination.

  1. (2 marks) Answer to the correct number of significant figures:

  2. (1 mark) The average distance between nitrogen and oxygen atoms is 115 pm in a compound called nitric oxide. What is this distance in millimeters?

  3. (2 marks) An automobile uses gasoline at a rate of 36.8 mi/gal, which is the same as ________ km/L. Note: 1 km = 0.6214 mi, 1 gal = 3.78 L

  4. (3 marks) A student prepared a stock solution by dissolving 20.0 g of KOH in enough water to make 150. mL of solution. She then took 15.0 mL of the stock solution and diluted it with enough water to make 65.0 mL of a final solution. What is the concentration of KOH for the final solution?

  1. (10 marks) Aluminum metal and aqueous silver nitrate react according to the following balanced equation: Al ( s ) + 3 AgNO 3 ( aq )  3 Ag ( s ) + Al(NO 3 ) 3 ( aq ) In an experiment, 1.726 g of aluminum metal is mixed with 250. mL of 0.366 M silver nitrate solution. a) What is the limiting reagent? Show your work. b) How many grams of the excess reactant remain after the reaction is complete? c) If 7.2 g of silver metal is collected after the reaction, what was the percent yield of this reaction?
  1. (4 marks) Dibutyl succinate is an insect repellent used against household ants and roaches. Its composition is 62.58% C, 9.63% H, and 27.79% O. What is the empirical formula?

  2. (9 marks) Determine the number of milliliters of 0.00358 M phosphoric acid required to neutralize 25.00 mL of 0.00203 M calcium hydroxide. Be sure to include the balanced molecular equation.

  1. (6 marks) Concisely (one or two sentences) explain what is meant by three (3) of the following: a) stoichiometry b) reducing agent c) titration d) base e) precipitation reaction

Stoichiometry = mass to mole relationships used in chemical calculations

General scheme is: given n = m/MM mol ratio desired m = n x MM

Reducing agent = a substance that cause a reduction by donating an electron

  • allows another chemical to be reduced
  • species itself is oxidized
  • gives up electron(s)

Titration = an analytical procedure for determining the concentration of an unknown

solution

  • mole – volume – concentration calculations (solution stoichiometry)

General scheme is: given n = C x V mol ratio desired C = n/V

Base = a substance that provides hydroxide (OH-) ions when dissolved in water

Precipitation reaction = a reaction in which an insoluble solid precipitate forms from

the mixture of two soluble aqueous solutions

Bonus:

Answer the following about the periodic table:

a) The elements of the periodic table can be categorized into three groups. What are the names of these groups? i) What are the properties of the elements in these groups? b) What are the columns of the periodic table called? i) How are the elements in the same column related? c) What are the rows of the periodic table called?

a) Metals, non-metals, and metalloids (semi-metal) i) Metals are found in the lower left side and middle of the periodic table and share common properties – they are good conductors of heat and electricity, they can be pounded into flat sheets (malleability), they can be drawn into wires (ductility), they are often shiny (called a metallic luster), and they tend to lose electrons when they undergo chemical changes. ii) Nonmetals are found in the upper right side of the periodic table. The dividing line between metals and nonmetals is the zigzag diagonal line running from boron to astatine. Nonmetals have varied properties – some are solids at room temperature, others are liquids or gases – but as a whole, they tend to be poor conductors of heat and electricity and they all tend to gain electrons when they undergo chemical changes. iii) Metalloids exhibit mixed metal and nonmetal properties. In most respects, metalloids behave as nonmetals, both chemically and physically. However, in their most important physical property, electrical conductivity, they sometimes resemble metals. Several metalloids are classified as semiconductors because of their intermediate (and highly temperature dependent) electrical conductivity. b) Columns in the periodic table are called groups or families i) Elements in the same group have similar chemical properties c) Rows in the periodic table are called periods

Q1 Q2 Q3 Q4 Q5 Q6 Q7 Q8 Q9 Q10 BONUS TOTAL