Regents Chemistry Review Packet for Midterm Exam 2012-2013

Regents Chemistry Review Packet for Midterm Exam 2012-2013

Name:

Significant Figures

How many sig figs are in each of the following measurements?

1.  6.25x10-6 g _____3_____ 6. 86270 mm ____4______

2.  5.505x102 cm _____4_____ 7. 86270.0 mm ____6______

3.  0.0081 L _____2_____ 8. 140 m/hr ____2______

4.  87.0˚C _____3_____ 9. 729 s ____3______

5.  0.00750 dm3 _____3_____ 10. 13.90 ml ____4______

Vapor Pressure

1.  What is vapor pressure?

pressure exerted by a vapor above a liquid

2.  How is vapor pressure related to boiling point?

Normal boiling point of a liquid is the temp at which the vapor pressure of the liquid is equal to the standard atmospheric pressure

3.  If a substance has a high vapor pressure and a low boiling point what can you say about the IMF?

IMF are weak

4.  What variable does vapor pressure depend on?

temperature

Nuclear Chemistry

Identify each of the following as natural transmutation (NT) or artificial transmutation (AT); if AT identify if can be fission or fusion. Explain how to identify which type of reaction it is.

8. We use two laws to balance nuclear equations. These two laws are the conservation of ______

atomic number ___ and the conservation of ___atomic mass___.

9. In the symbol 31H what does the 3 represent? ____atomic mass______

10. In the symbol 126C what does the 6 represent? ___atomic number____

11. What nuclide is a radioisotope used to date rocks? ___U-238___

12. Find the missing term in the following nuclear equations:

a.  209F → 0-1e + X X = ___2010Ne____

b.  18079Au → 17677Ir + X X = ___42He_____

c.  X → 0-1e + 3719K X = ___3718Ar____

d.  94Be + X →126C + 10n X = ____42He______

13. For fusion reactions to occur, high temperatures are required because both of the reacting nuclei have

a. a large mass

b. many neutrons

c. a positive charge

d. a negative charge

14. Name one beneficial use and one destructive use of nuclear fission reactions?

Beneficial: large amounts of energy with no greenhouse effect

Destructive: exposure to harmful radiation and nuclear waste to dispose of

15. Explain why it is more difficult to cause an artificial transmutation reaction with an alpha

particle than with a neutron.

Alpha particles have a positive charge so need to be accelerated to high speeds in order to overcome the repulsion forces of (+) to (+) particles for the nuclear reaction to occur

16. Where in the universe do fusion reactions take place?

The sun

17. Where do fission reactions take place in a controlled fashion? In an uncontrolled one?

Controlled: nuclear power plant Uncontrolled: nuclear bomb

18. What is the total number of neutrons in an atom of Pb-207? __207-82 = 125 neutrons_

19. What is the nuclear charge of fluorine? ____+9 (9 protons) ______

20. What happens to the half-life of a radioactive substance as the temperature of the substance

increases? ____ no change ______

21. Based on Reference Table N, what fraction of a sample of gold-198 remains radioactive after

2.69 days?

HL Au-198 is 2.69 days after I half-life there will be ½ of the sample left

22. How many days are required for 200.0 grams of radon-222 to decay to 50.0 grams?

HL Rn-222 = 3.82 days 200 → 100 → 50 2 half-lifes = (3.82 days)(2) = 7.64 days

23. How much time must elapse before 16 grams of potassium-42 decays, leaving 2 grams of the

original isotope?

HL K-42 = 12.4 h 16 → 8 → 4 → 2 (12.4 h)(3 HL) = 37.2 h

24. The half-life of iodine-131 is 8.07 days. What fraction of a sample of I-131 remains

after 24.21 days?

24.21 days = 3 HL 1 → 1 → 1

8.07 days 2 4 8

25. What was the original mass of a radioactive sample that decayed to 25 grams in 4 half-lives?

1 2 3 4

400g → 200g → 100g → 50g → 25g 400 g was original mass

Atomic Structure

1.  What is the definition of each of the following terms:

a.  Atomic number = number of protons

b.  Mass number = number of proton plus number of neutrons

c.  Isotope = two (or more) atoms of the same element with different # neutrons (so have different mass numbers) examples: 146C and 136C and 126C

d.  Nucleon = term used to collectively indicate the protons and neutrons in the nucleus

2.  What is the charge, mass, location, and symbol of each of the following subatomic particles?

3.  The number of electrons in a neutral atom is equal to the number of __protons____

4.  Complete the following table:

5.  What is the charge on the nucleus of an atom? ____positive______.

6.  Most of the volume of an atom is ____empty space______.

7.  Describe Rutherford’s famous experiment. What were the two results of the experiment and what conclusion did Rutherford draw from each result?

1. positively charged part of atom is very small and is located in the center of the atom

2. majority of the atom is empty space

8.  What is the difference between an isotope and an ion?

Isotopes are 2+ same atoms with different # neutrons

Ions are atoms that are charged due to losing/gaining electrons

9.  Given that chlorine is 75% Cl-35 and 25% Cl-37, calculate the average atomic mass of chlorine.

(.75)(35) + (.25)(37) = 35.5 amu

10.  What radioactive isotope is used to date organic material (wool, linen, wood, bones, etc)?

C-14

11.  What is the absolute temperature scale?

Kelvin

12.  In the Bohr model of the atom, describe the type of electron transition which will result in the production of a spectral line. Is this transition endothermic or exothermic?

electrons transitioning from higher energy levels to lower energy levels emit wavelengths of light (bright line spectra) - this is an exothermic process since energy is emitted

13.  How many atoms are represented in the formula (NH4)2SO4?

2 atoms of N, 8 atoms of H, 1 atom of S, 4 atoms of O for a total of 15 atoms

14.  What are two common substances that sublime?

CO2(s) [carbon dioxide] and I(s)

Periodic Table

1.  What is nuclear charge? What is effective nuclear charge?

·  Nuclear charge is the charge of the nucleus = positive sign with # protons in nucleus

- example: nuclear charge of K is +19

·  Effective nuclear charge: charge felt by valence electrons

o  Calculate: # protons minus # kernel electrons

2.  What is ionization energy?

amount of energy needed to remove the most loosely held electron (valence)from an atom

3.  What is electro negativity?

ability of an atom to hold onto its own electrons & attract its neighbor’s electrons

4.  What are the trends for atomic size, ionization energy, & electro negativity in the Periodic Table?

·  Atomic size ↑ as go down a column from top to bottom and ↓ as go left to right across a row

·  electro negativity increases from bottom left (Fr) to upper right (F)

·  ionization energy ↓ as go down a column from top to bottom and ↑ as go left to right across a row

Energy Changes: Identify the Q equation needed to solve each of the following energy word problems below, then solve each problem.

1.  How much energy is required to heat a 35.0 g sample of water from 35ºC to 75ºC?

Equation:____Q = mcΔT______

Q = (35.0g)(4.18J/gºC)(40 ºC) = 5,852 J

2.  An ice cube at 0˚C with a mass of 175.0g melts. How much energy does the ice absorb to melt?

Equation: ____Q = mHf______

Q = (175.0g)(334J/g) = 58,450 J

3.  An 85.0g sample of water at 100.0˚C boils. How much energy is required to convert the water to steam at 100.0˚C?

Equation: ____ Q = mHv ______

Q = (85.0g)(2260J/g) = 192,100 J

4.  A sample of water with a mass of 160.0g is heated from 15.0˚C to 70.0˚C. How much energy is required to heat the water?

Equation: _____ Q = mcΔT ______

Q = (160.0g)( 4.18J/gºC)(55ºC) = 36,784 J

5.  450.0g of water at 0.0˚C is frozen to ice at 0.0˚C. How much energy is released to the environment?

Equation: ______Q = mHf ______

Q = (450.0g)(334J/g) = 150,300 J

6.  200.0g of steam at 100.0˚C condenses to water at 100.0˚C. How much energy is released to the environment?

Equation: ____ Q = mHv ______

Q = (200.0g)(2260J/g) = 452,000 J

7.  A 225g sample of water is cooled from 95.0˚C to 40.0˚C. How much energy is released to the environment?

Equation: _____ Q = mcΔT ____

Q = (225g)(4.18J/gºC)(-55ºC) = (-) 51,727.5 J

8.  A block of ice at 0.0˚C with a mass of 1.0kg melts. How much energy is absorbed from the environment to convert it to water at 0.0˚C?

Equation: ____ Q = mHf______

Q = (1000g)(334J/g) = 334,000 J

9.  A 200.0g sample of water at 100.0˚C is boiled and converted to steam at 100.0˚C. How much energy is required?

Equation: _____ Q = mHv______

Q = (200.0g)(2260J/g) = 452,000 J

10.  A 345.0g sample of steam at 100.0˚C condenses to water at 100.0˚C. How much energy is released to the environment?

Equation: ____ Q = mHv______

Q = (345.0g)(2260J/g) = 779,700 J

11.  If you carry out a reaction in a Styrofoam cup calorimeter and

a.  the temperature of the water increases, is the reaction endothermic or exothermic?

b.  the temperature of the water decreases, is the reaction endothermic or exothermic?

c.  How would you calculate the energy change? Q = mcΔT

Phase Changes

1.  _temperature_ is a measure of the average kinetic energy of the particles of a substance.

2.  _vaporization_ is another word for boiling.

3.  _heat of fusion_ is the amount of energy required to melt one gram of a solid at its melting point.

4.  _fusion__ is another word for melting.

5.  One type of physical change is a _phase change___.

6.  Solid to liquid or gas is an example of an _endothermic__ process.

7.  __evaporation__ is the spontaneous change from liquid to gas at any temperature.

8.  __sublimation__ is the change from solid phase to gas phase.

9.  The average kinetic energy of the particles of a substance is increasing when the temperature is ___increasing______.

10.  __gas__ takes the shape and volume of its container.

11.  __boiling__ is the change from liquid phase to gas phase at a constant temperature.

12.  __condensation_ is a change from gas to liquid phase which is noticeable on glass.

13.  __melting___ is the change from solid to liquid phase at a constant temperature.

14.  __heat of vaporization__ is the amount of energy required to convert one gram of a liquid to the gas phase at its boiling point.

15.  __deposition_ is the change from gas phase to the solid phase.

16.  __solid__ has a definite shape and a definite volume.

17.  Gas to liquid or solid is an example of an _exothermic__ process.

18.  When the temperature is constant, the average kinetic energy of the particles in a substance is ___constant____.

19.  __liquid__ has definite volume and indefinite shape.

20. When temperature decreases, the average kinetic energy of the particles of a substance is __decreasing___.

Mole Math

1.  Draw the mole map in the space below

2.  Calculate the formula mass of the following:

a.  NH3__ 1(14) + 3(1) = 17g/mol__ d. CH4 _1(12) + 4(1) = 16g/mol__