Chemistry Final ExamVersion 12/2016

Name: Kirstan

Student number:

Directions: It is important that you provide answers in your own words. Please focus only on information from the text/eBook to create your own solutions. Please do not use direct information from an outside source (especially copying and pasting from an “answer” website). Use of direct information from an outside sourceis against school policy.All answers will be checked for plagiarism. Instances of plagiarismcan resultin probation or possible dismissal from the school.

Please be sure to follow all guidelines (number of sentences/showing all calculations) and to provide the correct metric units of measure. All questions are 3.33 points each (.33 for unit)

  1. A student collected the following data for a fixed volume of gas:

Temperature (⁰C) / Pressure (mm of Hg)
10 / 726
20 / 750
40 / 800
70 / 880
100 / 960
150 / ???

Fill in the missing data point. Show all calculations leading to an answer.

P1/T1 = P2/T2

P1 = 726 mm Hg

T1 = 10 = 273.15 ( to get Kelvin )= 373.15 K

T2 = 150 + 273.15 = 423.15 K

P2 = 750 * 423.15 & then divide that by 293.15

317,362.5 / 293.15 = 1,082.59

1,082.58 rounded 1090 mm of Hg

  1. You are given a clear solution of KNO3. Using 3 – 4 sentences (in your own words) explain how you would determine if the solution is unsaturated, saturated or supersaturated.

To determine if the solution is saturated, unsaturated or supersaturated you would add more of the solute. And if the solute dissolves, the solution is unsaturated, if the solute does not dissolve, it is then saturated. Supersaturated means a solution with more dissolved solute than the solvent would normally contain. So, by adding more of the solute and if it forms into “crystals”(as what it would look like) and doesn’t dissolve is determined to be supersaturated.

  1. Explain why gasoline will not dissolve in water.

Gasoline is a non-polar molecule and non-polar solvents such as gasoline dissolve only with non-polar compounds. For example water and oil do not mix but oil and gasoline do because oil and gasoline are both non-polar molecules and water is a polar molecule.

  1. Explain in 3 – 4 sentences (in your own words) how perspiration helps keep you cool on a hot day.

For example, when your body is cold, it uses more energy to keep your body warm just like perspiration helps keep your body cool on a hot day. Perspiration is sweat or the action of sweating. Sweat is the heat released from the body. When sweat evaporates it removes heat and when the body is wet, it makes it feel cooler.

  1. You have two sealed jars of water at the same temperature. In the first jar there is a large amount of water. In the second jar there is a small amount of water. Using 3 -4 sentences explain how the vapor pressure of water in the first jar compares with the vapor pressure of water in the second jar.

As temperature increases pressure is lowered, pressure is impacted by temperature. More water in a container equals more pressure. If the pressure is less, it is more easier for water particles to escape and if greater is the rate of the evaporation taking place.

  1. Using 3 – 4 sentences explain (in your own words) why water expands when it freezes?

With liquid particles, they aren’t packed together like a solid but aren’t spaced out like a gas. When water is being frozen, the molecules are being locked into place. What causes the water to expand when frozen is the density of becoming a solid. A solid is most dense than any other state of matter. And a solid is compacted so when frozen the molecules are locked into place but becoming a solid also allows it to become more compacted which causes it to expand.

  1. Using your knowledge of colligative properties explain whether sodium chloride or calcium chloride would be a more effective substance to melt the ice on a slick sidewalk. Use 3 – 4 sentences in your explanation.

Colligative properties = the number of particels.

Number of ions for sodium chloride = 2

number of ions for calcium chloride = 3

Colligative properties is all about the number of particles something contains. The more ions a solution contains the faster it eats or dissolves the ice. So with that being said, sodium chloride has 2 ions and calcium chloride has 3 ions, so calcium would work more effectively to melt ice.

  1. When a 2.5 mol of sugar (C12H22O11) are added to a certain amount of water the boiling point is raised by 1 Celsius degree. If 2.5 mol of aluminum nitrate is added to the same amount of water, by how much will the boiling point be changed? Show all calculations leading to your answer OR use 3 – 4 sentences to explain your answer.

Al(NO3)3
Al(NO3)3 > Al3+ + 3NO3-
= 4 ions ( 4x of every sugar.)
the boiling point elevation of Al(NO3)3 = 1C*4 = 4C

  1. If 5.40 kcal of heat is added to 1.00 kg of water at 100⁰C, how much steam at 100⁰C is produced? Show all calculations leading to an answer.

5,400 cal divided by 79.5 cal/g

=67.9 g is the water that is produced

  1. The freezing of water at 0⁰C can be represented as follows:

H2O (l) ↔ H2O(s)

The density of liquid water is 1.00 g/cm3. The density of ice is 0.92 g/cm3. In 3 – 4 sentences explain why applying pressure causes ice to melt.

The higher the pressure the more energy that will be applied. And the more energy that is being applied to the ice causes it to melt. Due to more energy causes a rise in the temperature. A rise in the temperature is why ice melts.

  1. The Kw of water varies with temperature. Calculate the pH of water at 46⁰C with a Kw = 1.219 x 10-14. Show all calculations leading to an answer.

(H+) = (OH-)

(H+) (OH-) = Kw / temperature = 46 degrees C

H+ = square root of Kw (3.22 * 10^-14)

H+ = 1.80 * 10^-7

pH = -log

=-log (1.80 *10^-7)

= 6. 75 rounded up to 6.80

the pH = 6.5 in neutral water at 46 degrees C

  1. Calculate the hydroxide ion concentration of a solution with pH = 3.25. Show all calculations leading to an answer.

pH + pOH = 14

pOH = 14 -10.25 then that equals 3.75

pOH = -log (OH-) = 10^3.75 = 1.78 (rounded up = 1.8) *10^-4 M

  1. What salt results from the neutralization of phosphoric acid with potassium hydroxide?

H3Po4 + 3KOH > K3PO4 + 3H2O

  1. What is the oxidation number of chlorine in Al(ClO4)3?

Oxidation number of chlorine is 7.

the oxidation state is 3.

there’s 12 oxygen

-2 for each -24. then you take -24 + 3 = -12

there’s 3 Cl .

Need +21 to balance -21 = +21/3 = 7

  1. Which element is oxidized in the following reaction:

CuO(s) + H2 (g) Cu(s) + H2O (l)

Hydrogen is being oxidized due to it gaining another element and becoming a compound.

  1. Why must the number of electrons lost equal the number of electrons gained in every redox reaction? Use 3 – 4 sentences in your own words to address this question.

Balancing an equation is the whole point of balancing the loss and gain of electrons. If an element gains an electron then another element had to have lost it. A redox reactions or an oxidation-reduction reaction involves the transfer of electrons between two chemical types. The compound that loses an electron(s) is being oxidized and the one that gains electron(s) is being reduced. A redox reactions is using the purpose of balancing the equation of the reaction.

  1. The following unbalanced equation describes the reaction that can occur when lead (II) sulfide reacts with oxygen gas to produce lead (II) oxide and sulfur dioxide gas:

PbS + O2 PbO + SO2

Balance the equation and describe in words the electron transfer(s) that takes place.

2PbS + O2 > 2PbO + SO2

2Pbs + O2 > 2PbO + 2SO2

2PbS + 3O2 > 2PbO + 2SO2

(balance 6 oxygen and 2 oxygen ) so 6 divided by 2 = 3 = 3O2

Oxygen is reduced and sulfur is oxidized.

  1. What type of radiation is emitted when chromium-51 decays into manganese-51? Show the nuclear equation that leads you to this answer.

24/51 chromium ( chromium- 51/24 > manganese- 51/25 )

= 25/51 manganese (+ -1/0 e) = to beta rays.

= 24Cr51 + (-1/0 e) > 25Mn51

beta radiation ( chromium 51/ 25 ) - (manganese 51/25) + (+ -1/0 e) = to beta rays.

  1. A radioactive nucleus alpha decays to yield a sodium-24 nucleus in 14.8 hours. What was the identity of the original nucleus? Show the nuclear equation that leads you to this answer.

Aluminum = 13

Al –28 = is an isotope of Al.

Al = 15 neutrons

28/13 Al > 24/ 11 Na + 4/2 A

  1. Iron-59 has a half-life of 45.1 days. How old is an iron nail if the Fe-59 content is 25% that of a new sample of iron? Show all calculations leading to a solution.

(100/25) =0.693 (45.1)

25 =100 e^ (-.693 t/45.1)

t = -45.1/.693 (in .25)

t = 90.2 days.

  1. Using at least 3 to 4 complete content related sentences, explain how the compressed gas in an aerosol can forces paint out of the can. Be sure to describe how the gas pressure inside the can changes as the paint is sprayed. Please refer to figure 14.5 in lesson 14.1.

Compressibility is how much volume of mater decreases under pressure (from the text book page 450 ). Gases can be squeezed into small spaces but can be put closer together under pressure. The pressure inside of the new can is greater than the pressure outside of the can. When the nozzle is opened it lets pressure from the outside in, which forces the compacted pressure inside the can to force the paint up the tube. The more the can is used the less the pressure is or gets.

  1. pH is a measure of _____( hydrogen ion concentration )_____.

a. hydrogen ion concentration.c. hydroxide ion concentration.

b. hydrogen gas concentration.d. hydrolysis.

  1. A neutralization reaction between an acid and a base always produces ( salt and water )
  1. salt and acidic anhydride.c. water and basic anhydride.
  2. salt and basic anhydride.d. salt and water.
  1. If the pH of a solution is _( 7 )_ the solution is basic.

a. 2b. 5c. 7d. 10

25 – 30 Apply the appropriate word to the definition indicated. Not all words will be used.

25. enthalpy / Heat content of a system at constant pressure / calorie (cal)
26. energy. / Ability to do work / Chemical Potential Energy
27. entropy / Disorder / Energy
28. kinetic energy. / Energy of motion / Enthalpy
29. thermochemistry / Study of energy changes that ocrrue during chemic reaction and changes in states. / Entropy
30. specific heat. / Amount of heat required to raise T of 1 g of pure water 1◦C / Joule
Kinetic energy
Heat (q)
Specific Heat
Thermochemistry