Introduction to Experimentation - Final
The enthalpy of solution is defined as ∆Hsoln=∆Hsolute+∆Hsolvent+∆Hmix. Each of the terms on the right side of the equation are either endothermic or exothermic. Which answer properly depicts this. A) (Endothermic, Endothermic, Endothermic) B) (Endothermic, Endothermic, Exothermic) C) (Endothermic, Exothermic, Endothermic) D) (Exothermic, Endothermic, Endothermic) E) (Exothermic, Exothermic, Endothermic)
B) (Endothermic, Endothermic, Exothermic)
When 0.105 mol propane, C₃H₈ is burned in an excess of oxygen, how many moles of oxygen are consumed? The products are carbon dioxide and water. You have to properly balance the equation before you can answer this question. A) 0.420 mol O₂ B) 0.525 mol O₂ C) 0.875 mol O₂ D) 0.905 mol O₂ E) 0.975 mol O₂
B) 0.525 mol O₂
Furthermore, what is the mobile phase in this experiment? A) 10% 6M NaOH and 90% acetone B) 10% 6M HCl and 90% acetone C) 10% 5M KCl and 90% methanol D) 10% 5M KCl and 90% acetone
B) 10% 6M HCl and 90% acetone
Even though we are well into the course Dumbledore notices some of the students are still having trouble with significant figures. Let's review them once more: How many significant figures does the result of the following calculation have? (3.478-2.31)*(4.428-3.56) A) 1 B) 2 C) 3 D) 4 E) 5
B) 2
Now they feel it is best to have you identify an unknown gas based on its properties. Suppose 0.508 g of a gas occupies a volume of 0.175 L at a temperature of 25.0ºC is held at a pressure of 1.000 atm. What gas is this most likely? A) Neon B) Chlorine C) Fluorine D) Oxygen E) Krypton
B) Chlorine
As a first problem in this lesson, Dumbledore would like to know what chromatog- raphy means. This seems like a reasonable place to start. Which pair of words best describes chromatography? A) Time-Writing B) Color-Writing C) Sleep-Walking D) Time-Traveling
B) Color-Writing
Below you are presented with sets of quantum numbers: (n, l, ml, ms). Only one is a valid set. Which is it? A) (4,3,2,1) B) (3,3,2,1/2) C) (3,1,-1,-1/2) D) (2,0,0,0) E) (5,3,-4,1/2)
C) (3,1,-1,-1/2)
One of these subshells is not possible, which is it? A) 3d B) 4d C) 1p D) 4s E) 2s
C) 1p
Lastly, a suddenly formed bubble of vapor may eject the hot and perhaps corrosive contents violently from a test tube. What is this known as? A) Shafting B) Belching C) Bumping D) Nelching E) Crashing
C) Bumping
Now that Hermione understands empirical formulas she wants to teach Harry and Ron. What is the empirical formula for dibromoethane: C₂H₄Br₂ A) C₂H₄Br B) CH₂Br₂ C) CH₂Br D) C₂H₂Br₂ E) CHBr
C) CH₂Br
We now all know what chromatography means. Snape looks disapprovingly around the class, he's not convinced of this. Dumbledore assures him everyone has read the chapter... right? Now let's consider specifics of the experiment. In this experiment the stationary phase is made out of what? A) Polycarbonate B) Acetone C) Cellulose D) Glass beads
C) Cellulose
Dumbledore thinks the students are now confident with significant figures; Snape is not so confident of this... Begrudgingly Snape decides to move forward in his lesson. His next lesson is in naming ionic compounds. He presents his students with sodium hydrogen sulfate and potassium permanganate. Which pair of ionic formulas is correct for these two compounds? A) NaHSO₃, KMnO₄ B) NaHSO₂, KMnO₄ C) NaHSO₄, KMnO₄ D) NaHSO₄, KMnO₃ E) NaHSO₃, KMnO₃
C) NaHSO₄, KMnO₄
What is the process by which a solute forms a solution in a solvent. A) calisthenics B) bumping C) dissolution D) neutralization E) delineation
C) dissolution
Well, we might as well try a similar question. Magnesium metal reacts with hydrochloric acid to produce hydrogen gas and an aqueous solution of magnesium (II) chloride. What substance is being oxidized. A) H₂ (g) B) MgCl₂ (aq) C) HCl(aq) D) Mg(s)
D) Mg(s)
Ron Weasley is slightly clumsy and often makes mistakes. Today he needs to heat a test tube filled with a solution. Where should he apply heat to the test tube? A) Bottom of the test tube. B) Top of the test tube. C) Middle of the test tube. D) The point at which the solution is highest in the tube. E) Anywhere is fine.
D) The point at which the solution is highest in the tube.
A compound is found to contain only 24.5 g nitrogen and 70.0 g oxygen. What is the compounds empirical formula. A) NO B) NO₃ C) N₂O₃ D) NO₄ E) N₂O₅
E) N₂O₅
One container of Tums costs 4.00 dollars. Each container has eighty 1.00 g tablets. Assume each Tums is 40.0 percent CaCO₃ by mass. Using only Tums, you are required to neutralize 0.500 L of 0.400 M HCl. How much does this cost? Assume you are able to purchase individual tablets. Express your answer in dollars.
$1.25
Suppose one magnesium hydroxide tablet costs 0.0500 dollars. Let each 1.00 g magnesium hydroxide tablet be 100. percent magnesium hydroxide. Using only these tablets, you are required to neutralize 2.00 L of 0.500 M HCl. How much does this cost? Express your answer in dollars.
$1.50
Ollivander sells sheets of aluminum in a variety of thicknesses: 1.0 mm at 0.55 $/cm², 2.0 mm at 0.70 $/cm², and 3.0 mm at 0.85 $/cm² and various thicknesses in between all following the same linear trend. Harry needs 10.0 cm² of 2.2 mm thick aluminum. How much does this cost him? Express your answer in dollars.
$7.30
A 10.00 ml sample of an aqueous solution of calcium hydroxide is neutralized by 20.00 ml of 0.02000 M HNO₃(aq). What is the molarity of the calcium hydroxide solution?
0.0200 M
Suppose 53.0 mL of 0.320 M KOH is mixed with 28.0 mL of 0.250 M HNO₃. What is the concentration of OH⁻ ions after the reaction goes to completion? Express your answer in mol/L.
0.1229 mol/L
Suppose 13.00 mL of 0.100 M barium hydroxide is required to neutralize 17.00 ml of nitric acid with an unknown concentration. What is the concentration of the nitric acid. Express your answer in mol/L.
0.1529 M
A 1.00 L sample of a gas at 25.0ºC and 1.00 atm contains 50.0 % helium and 50.0 % neon by mass. What is the partial pressure of the neon. Express your answer in atmospheres.
0.167 atm
Snape grows tired of these conceptual questions and thinks it's time for a problem. What is the retention factor if the distance traveled by the solvent front is 2.00 cm, and the distance traveled by the ion is 0.40 cm?
0.20 cm
A student finds that 12.34 mL of a NaOH solution is needed to neutralize 0.5678 g of potassium hydrogen phthalate (KHC₈H₄O₄). What is the concentration of the NaOH solution? Express your answer in mol/L.
0.2255 mol/L
Let an n-protic acid be an acid that can donate n hydrogen ions and has the formula HₙX. If 0.600 L of 0.400 M sodium hydroxide is required to titrate 0.400 L of a 0.300 M HₙX to the equivalence point, what is n in HₙX?
0.240 mol
Dumbledore is pleased with your progress. Snape is, as always, somewhat indifferent. However, they both feel a gas phase density problem should come next. Calculate the density of helium gas at 25.0ºC and at a pressure of 1521 mmHg. Express your answer in g/L.
0.327
How many grams of oxalic acid dihydrate H₂C₂O₄·2H₂O, a diprotic acid, are needed to react with 20.00 mL of 0.4500 M NaOH.
0.5673 g
Suppose the gas resulting from the sublimation of 1.00 g carbon dioxide is collected over water at 25.0ºC into a 1.00 L container. What is the total pressure in the container? Express your answer in atmospheres.
0.587 atm
Severus Snape needs to know how much water is in a sample for his potions class. Calculate the percent of water in a sample if before dehydration the sample weighed 1.972 g, and 1.641 g after dehydration.
16.78%
What volume of 0.210 M sulfuric acid is required to completely react with 2.14 g aluminium hydroxide?
196 mL
Dumbledore decides to gives a surprise demonstration. He starts with a hydrate of Na₂CO₃ which has a mass of 4.31 g before heating. After he heats it he finds the mass of the anhydrous compound is found to be 3.22 g. He asks everyone in class to determine the integer x in the hydrate: Na₂CO₃·xH₂O; you should do this also. Round your answer to the nearest integer.
2
How many unpaired electrons would you expect on Vanadium in V2O3?
2
Starting with 5.00 g barium chloride n hydrate yields 4.26 g of anhydrous barium chloride after heating. Determine the integer n. Round your answer to the nearest integer.
2
Let 4 moles of methanol (liquid) combust in 3 moles of gaseous oxygen to form gaseous carbon dioxide and water vapor. Suppose this occurs in a chamber of fixed volume and fixed temperature. If the original pressure is 1.0 atm, what is the final pressure in the chamber. Express your answer in atm.
2 atm
A container, with a fixed volume, filled with a fixed amount of an ideal gas has an original pressure of 2.00 atm at 30.0ºC. What is the pressure if the temperature is increased to 50.0ºC. Express your answer in atmospheres.
2.13 atm
Suppose a solution is prepared by dissolving 15.0 g NaOH in 0.150 L of 0.250 M nitric acid. What is the final concentration of OH⁻ ions in the solution after the reaction has gone to completion. Assume that there is no volume change when adding the grams of NaOH.
2.25 M
How many millilitres of 0.250 M NaOH are required to neutralize 0.150 g of oxalic acid dihydrate H₂C₂O₄·2H₂O.
9.5 mL
Let's say you hold some ice in your hand. The ice melts and your hand feels cold. Is the reaction H₂O(s)→H₂O(l) endothermic or exothermic? Is the change in enthalpy of the reaction positive or negative. A) (endothermic, positive) B) (endothermic, negative) C) (exothermic, positive) D) (exothermic, negative)
A) (endothermic, positive)
Hermione now understands how the affinity of the complex and the stationary phase affects the velocity of the complex. She is curious though, what in the stationary phase is controlling this. Fill in the blank: The paper in the paper chromatography lab is made of cellulose which has a surface covered in groups. A) -OH B) -CH3 C) -NH D) -NH2
A) -OH
Prof. Dumbledore is concerned that Harry, Ron and a few other students are still having some difficulties with significant figures. Hermione seems to have gotten it though. Why don't we try to review them. How many significant figures does the result of the following expression have? (6.635-1.321)*(1747.4)*(3.54-2.6). A) 1 B) 2 C) 3 D) 4 E) 5
A) 1
How many unpaired electrons would you expect on iron in [Fe(H₂O)₆]³⁺?
5
Hydrates take the form: compound·nH₂O. An unknown hydrate has a molar mass of 190. g/mol. If the anhydrate has a molar mass of 100. g/mol, what is the integer n in the hydrate.
5
Ron and Hermione begin with 1.50 g of the hydrate copper(II)sulfate·x-hydrate (CuSO₄·xH₂O), where x is an integer. Part of their practical exam is to determine this integer x. They are working in pairs, though Hermione is doing most of the work. This should be discouraged! After dehydration they find that they are left with 0.96 g of the an-hydrate CuSO₄. What is the unknown integer x. Round the answer to the nearest integer.
5
Trevor, Neville Longbottom's pet toad, has a mass of 13.6 kg. Trevor jumps into a large cylinder containing water. The water level rises 2.50 L. What is the density of the toad? Express your answer in kg/L.
5.44 kg/L
Suppose Harry begins with the hydrate KAl(SO₄)₂·12H₂O. After dehydration he finds that he is left with 3.0 g of the an-hydrate KAl(SO₄)₂. How many grams did he start with?
5.5
Let's try one more but add the theoretical yield concept. Consider the following UNBALANCED equation: NO(g) + H₂(g) → NH₃(g) + H₂O(g) If you start with 89.3 g NO(g) and 28.6 g H₂(g), find the theoretical yield of ammonia. Express your answer in grams.
50.7
You are in space and running out of water. You do have a great deal of magnesium carbonate pentahydrate. It is possible to extract the water from this. Determine the percent of water by mass in the hydrate magnesium carbonate pentahydrate (MgCO₃·5H₂O).
52%
Mr. Finnigan has a particular proclivity for pyrotechnics. He will use right circular cylinders with a height of 12.0 cm and a radius of 11.6 cm. If the density of his powder is 8.41 g/cm³, how many grams of powder does he need to stop the Snatchers from getting to Hogwarts if he needs 14 of these cylinders? Express your answer in kg.
598 kg
For every 5.00 mL of milk of magnesia there are 400. mg of magnesium hydroxide. How many mL of milk of magnesia do we need to neutralize 40.0 mL of 0.500 M HCl? Express your answer in mL.
7.30 mL
How many unpaired electrons would you expect on aluminum in aluminum (III) oxide?
0
Solid potassium chlorate decomposes into solid potassium chloride and oxygen gas. If 2.00 g potassium chlorate decomposes in a chamber with a fixed volume of 0.800 L, and temperature of 25.0ºC. What is the final chamber pressure. Assume all the potassium chlorate decomposes. Express your answer in atmospheres.
0.748 atm
At this point Ron is slightly confused, this isn't surprising. However, Hermione is doing rather well with them. This also isn't surprising since she studies every day, as should all students. She feels she can help him understand these problems by working with him though another: A 1.00 L sample of dry air contains 0.0319 mol N₂, 0.00856 mol O₂, and 0.000381 mol Ar. If temperature is 25.0ºC what is the partial pressure of N₂? Express your answer in atmospheres.
0.78 atm
Suppose you titrate 80.0 mL of 2.00 M NaOH with 20.0 mL of 4.00 M HCl. What is the final concentration of OH⁻ ions.
0.8 M
Lastly, Snape thinks we should try one more calculation. What is the retention factor if the distance traveled by the solvent front is 2.0 cm, and the distance the ion is from the solvent front is 0.20 cm? Hint: Be careful with how Snape worded this question.
0.90 cm
Calculate the density of nitrogen gas at a temperature of 101ºC and at a pressure of 1.00 atm. Express your answer in g/L.
0.913 g/L
Calculate the height of a column of carbon tetrachloride, CCl₄(l), with a density of 1.59 g/mL that exerts the same pressure as a 15.2 cm column of Mercury, Hg(l), that has a density of 13.6 g/ml. Express your answer in meters.
1.30 m
What is the pressure exerted by 0.801 mol of CO2 in a 13.0 L container at 298 K? Express your answer in atm.
1.51 atm
Suppose you have a piston in a cylinder where the gas temperature is 26.0ºC and has a volume of 1.75 L. What is the volume of the gas if you move the assembly to a cooler region with a temperature of 3.00ºC? Assume the gas pressure within the cylinder is constant. Express your answer in L.
1.62 atm
To begin with Snape thinks we should review an ideal gas problem. What is the pressure exerted by 0.703 mol O₂ in a 11.0 L container at 314 K. Express your answer in atmospheres.
1.64 atm
Suppose we now collect hydrogen gas, H2(g), over water at 21◦C in a vessel with total pressure of 743 Torr. If the hydrogen gas is produced by the reaction of aluminum with hydrochloric acid: 2Al(s) + 6HCl(aq) → 2AlCl₃(aq) + 3H₂(g) what volume of hydrogen gas will be collected if 1.35 g Al(s) reacts with excess HCl(aq)? Express your answer in liters.
1.85 L
Now that Snape and Dumbledore has taught you the finer points of hydration calculations they have a slightly more challenging problem for you. Suppose you dissolve 52.2 g of Na₂CO₃·xH₂O in enough water to make 5.00 L of solution. The final concentration of the solution was found to be 0.0366 M. Determine the integer x in the hydrate: Na₂CO₃·xH₂O. Round your answer to the nearest integer.
10
What is the maximum number of electrons can a d subshell can hold?
10
How many millilitres of 0.200 M NaOH are required to neutralize 20.0 ml of 0.100 M HCl?
10 ml
Suppose you begin with an unknown volume of 8.61 M H₂SO₄ and add enough water to make 5.00*102 mL of a 1.75 M H₂SO₄ solution. What was the unknown volume of your 8.61 M H₂SO₄ solution that you began with? Express your answer in mL.
102 mL
Calculate the density of rock that weights 14.5 kg and has a volume of 141 cm³. Express your answer in g/cm³.
103 g/cm³
Ron was able to get the previous problem right! Hopefully so were you. Now, as a small extension to the previous problem Snape asks everyone to calculate the mass of chlorine in 21 kg of C₂F₃Cl₃. Express your answer in kg.
12 kg
A sample of 88.0 g CO₂ is held at 291 K in a 40.0 L container. What is the pressure this gas exerts on the container. Express your answer in kPa.
121 kPa
Suppose hydrochloric acid reacts with potassium sulfite yielding water, sulfur dioxide, and potassium chloride. Suppose 4 moles of hydrochloric acid react with excess potassium sulfite. How many grams of sulfur dioxide are produced?
128 g
Suppose 50.0 mL of 0.350 M lithium hydroxide is mixed with 30.0 mL of 0.250 M perchloric acid. What is the pH of the resulting solution, assume the reaction goes to completion.
13.1
A flask of fixed volume contains 1.00 mole of gaseous carbon dioxide and 88.0 g of solid carbon dioxide. The original pressure and temperature in the flask is 1.00 atm and 300. K. All of the solid carbon dioxide sublimes. The final pressure in the flask is 2.75 atm. What is the final temperature in kelvins? Assume the solid carbon dioxide takes up negligible volume.
275 K
The philosopher's stone weighs 43.2 g is placed in a graduated cylinder containing 63 mL of water. After the stone is added to the cylinder the water rises to 74 mL. What is the density of the stone? Express your answer in g/mL.
3.9 g/mL
All faculty members are happy to see students help each other. Dumbledore is particularly pleased with Hermione. Though, it should be mentioned that students should not simply copy off each other. You will not learn anything that way. Snape glares at Ron... Ron slouches in his chair. Snape thinks it's time for a harder problem. How many milligrams of magnesium reacts with excess HCl to produce 31.2 mL of hydrogen gas at 754 Torr and ºC. The hydrogen is produced by the following reaction: Mg(s) + 2HCl(aq) → MgCl₂(aq) + H₂(g) Express your answer in milligrams.
30.3 mg
The antacid component of Tums is calcium carbonate. Assume Tums is 40.0 percent CaCO₃ by mass. If we have 400. mg of Tums how many ml of 0.100 M HCl can we neutralize? Express your answer in mL.
32 mL
A 0.272 g sample of a diprotic acid H₂X is titrated to the equivalence point. What is the molar mass of H₂X if 40.0 mL of 0.400 M NaOH is required. Assume both protons of the acid were titrated. Express your answer in g/mol.
34.0 g/mol
Suppose you have 0.100 m³ of CO₂, at pressure of 2.00 atm, and a temperature of 30.0ºC. How many grams of CO₂ do you have? Express your answer in grams
354 g
Though wizards might be able to manage without air-bags, Muggles certainly need them! Air-bags can be inflated by the decomposition of sodium azide, NaN₃. At 25.0◦C and 1.10 atm, what volume of N₂(g) is produced by the decomposition of 71.4 g NaN₃ under the following chemical reaction: 2NaN₃(s) → 2Na(l) + 3N₂(g) Express your answer in liters.
36.6 L
In attempts to lift Ron's spirits, Dumbledore asks him a fairly easy question: calculate the mass percent composition of carbon in C₂H₅Cl. Prof. Vitarelli thinks you should try this also.
37.2%
How many unpaired electrons would you expect on iron in iron II sulfide?
4
Harry's Golden Snitch, the smallest ball in Quidditch, is a sphere with radius of 3.10 cm, and a density of 6.12 g/cm³. What is its mass? Express your answer in grams.
764 g
A sample of an ideal gas is held at a constant temperature occupies 899 mL at 708 Torr. What pressure does the gas exert on its container if the volume is decreased by 10 percent. Express your answer in Torr.
787 Torr
4.0 moles of NaOH, a strong base, will completely dissociate in water. How many total moles of ions will it form.
8 mol
Harry's spell book is a rectangular solid and has dimensions 4.0 cm by 13 cm by 9.2 cm and a mass of 4.2 kg. What is its density? Express your answer in g/cm³.
8.8 g/cm³
A monoprotic acid is an acid that donates a single proton to the solution. Suppose you have 0.140 g of a monoprotic acid dissolved in 35.0 mL of water. This solution is then neutralized with 14.5 mL of 0.110 M NaOH. What is the molar mass of the acid?
87.8 g/mol
Ron Weasley isn't the best experimentalist. After an experiment he ends up with only 3.10 g of product. However, the same reaction has is a theoretical yield of 3.50 grams of product. What is the percent yield?
88%
Now that we understand the basics, Snape wants you to consider the following UNBALANCED equation: Al(s)+HCl(aq) → AlCl₃(aq)+H₂(g). Assume you have plenty of HCl and 6.0 mol of Al. How many moles of H₂ are formed? Express your answer in moles.
9 mol
Severus Snape knows that density of his powder is 3.00 g/cm³. He also knows he needs 3.00 cm³ of this powder. What mass in grams does he require?
9.00 g
Hermione Granger uses her Time-Turner and is suddenly whisked away to a cold April night in 1912 in the middle of the Atlantic ocean. She is on the Titanic enjoying the party. In the distance she sees a large white object approaching the ship. She thinks its pretty and not much danger to the ship so she carries on with her festivities. Later the large white object (an iceberg) hits the ship, and the ship begins to sink. As the ship is sinking she thinks, hmm, it wasn't that big of an ice-berg (and of course this ship cant sink...). What percentage of the iceberg was under water? Let the density of the water be 1.0 g/cm³, and the density of the ice be 0.92 g/cm³. Express your answer as a percentage (not a decimal).
92%
Let's try one more. What is the correct net ionic equation when CaCl2(aq) is mixed with AgNO3(aq)? A) Ag⁺(aq)+Cl⁻(aq) → AgCl(s) B) Ca²⁺(aq)+2NO₃⁻ (aq) →Ca(NO₃)₂(s) C) Ag⁺(aq)+NO₃⁻ (aq)+Ca²⁺(aq)+Cl⁻(aq) → AgCl(s)+Ca(NO₃)₂(s) D) No precipitate; no reaction. E) 2Ag⁺(aq)+2NO₃⁻ (aq)+Ca²⁺(aq)+Cl⁻(aq) → 2AgCl(s)+Ca(NO₃)₂(s)
A) Ag⁺(aq)+Cl⁻(aq) → AgCl(s)
Let's try one more. What is the molecular equation for the reaction of solid calcium carbonate with aqueous acetic acid. A) CaCO₃(s)+2CH₃COOH(aq) → Ca(CH₃COO)₂(aq)+H₂O(l)+CO₂(g) B) CaCO3(s)+2CH3COOH(aq) → Ca(CH₃COO)₂(s)+H₂O(l)+CO₂(g) C) CaCO₃(s)+CH₃COOH(aq) → CaCH₃COO(aq)+H₂O(l)+CO₂(g) D) CaCO₃(s)+CH₃COOH(aq) → CaCH₃COO(s)+H₂O(l)+CO₂(g)
A) CaCO₃(s)+2CH₃COOH(aq) → Ca(CH₃COO)₂(aq)+H₂O(l)+CO₂(g)
Dumbledore explains that a spectator ion is an ion which is not involved in the reaction under consideration. Though Snape thinks you all should know this... Sometimes it seems Snape would rather be teaching another class... or even be head of the school... Anyway, which is a spectator ion involved in the reaction of K2CrO₄(aq) and Ba(NO₃)₂(aq)? A) K⁺ B) Ba²⁺ C) CrO₄²⁻ D) NO²⁻ E) There are no spectator ions
A) K⁺
As a follow up question, which can Severus use? That is, which one of the following is soluble in water. A) NH₃ B) PbCl₂ C) PbI₂ D) BaCO₃ E) AgCl
A) NH₃
Now that we know what spectator ions are; we must also know they don't appear in the net ionic equation. Which is the correct net ionic equation for the reaction of CaBr2 (aq)+Na₂ SO₄ (aq). A) SO₄²⁻(aq)+Ca2⁺(aq) → CaSO₄ (s) B) Br⁻(aq)+Na⁺(aq) → NaBr(s) C) 2 Br⁻(aq)+Na⁺(aq) → NaBr₂(s) D) Br⁻(aq)+2Na⁺(aq) → Na₂Br(s) E) There is no precipitate that forms.
A) SO₄²⁻(aq)+Ca2⁺(aq) → CaSO₄ (s)
Snape next discusses molecular equations. He mentions that a molecular equation is also known as a complete-formula equation. The term molecular equation is somewhat misleading since the compounds are often formula units of ionic compounds and not molecular. Which is the correct molecular equation for the reaction of aqueous zinc II nitrate and aqueous sodium hydroxide. Note: a precipitate will form. A) Zn(NO₃)₂(aq)+2NaOH(aq) → Zn(OH)₂(s)+2NaNO₃(aq) B) Zn(NO₃)₂(aq)+2NaOH(aq) → Zn(OH)₂(aq)+2NaNO₃(s) C) ZnNO₃(aq)+2NaOH(aq) → Zn(OH)₂(s)+2NaNO₃(aq) D) ZnNO₃(aq)+2NaOH(aq) → Zn(OH)₂(aq)+2NaNO₃(s)
A) Zn(NO₃)₂(aq)+2NaOH(aq) → Zn(OH)₂(s)+2NaNO₃(aq)
In this experiment we have hydrated ions traversing the stationary phase. Hermione is curious why certain ions travel at different rates though the stationary phase. Fill in the blank: The more highly charged the complex (hydrated ion), the the affinity for the more polar stationary phase and the the ions move? A) greater, slower B) smaller, slower C) greater, faster D) smaller, faster
A) greater, slower
Which of the following anions would you expect to be paramagnetic? A. As²⁻ B. S²⁻ C. P³⁻ D. N³⁻ E. Si⁴⁻
A. As²⁻
As a final problem for the week Snape thinks we should incorporate something from a previous week, hydrates perhaps. Suppose we have a compound that is 4.330 % Li, 22.10 % Cl, 39.89 % O, and 33.69 % H2O. What is the compounds formula? A. LiClO₄ · 3 H₂O B. LiCl₂O₃ · 5 H₂O C. Li₂Cl₂O₃ · 5 H₂O D. Li₂Cl₂O₃ · 4 H₂O E. LiClO₃ · 4 H₂O
A. LiClO₄ · 3 H₂O
A ring weighing 9.45 g is placed in a graduated cylinder containing 25.3 mL of water. After the ring is added to the cylinder the water rises to 27.4 mL. What metal is the ring made out of? Assume the ring is a single metal. A. Titanium B. Copper C. Iron D. Lead E. Aluminum
A. Titanium
Looking at the bottom of her tea cup, Prof. Trelawney suddenly has a revelation! She knows one of the previous exam questions! She bursts into the class and and yells: Analysis of a sample is finds it contains 15.0% of species X, by mass, 75.0% of species Y, and 10.0% of species Z, by mass. The molar mass of species X is 45.0 g/mol, the molar mass of species Y is 150. g/mol, and the molar mass of species Z is 30.0 g/mol. If the molar mass of the sample is 1200 g/mol, what is the molecular formula of the sample? Prof. Vitarelli frowns at her disapprovingly. A. X₄Y₆Z₄ B. X₄Y₅Z₄ C. X₃Y₆Z₃ D. X₄Y₄Z₄ E. X₂Y₅Z₂
A. X₄Y₆Z₄
As an introduction to his class, Severus Snape teaches the first years at Hogwarts about hydrates. He begins with equations representing various dehydrations. Which of the following equations properly represents the dehydration of MgCO₃·5H₂O? A) MgCO₃ · H₂O(s) → MgCO₃(s)+H₂O(g) B) MgCO₃ · 5H₂O(s) → MgCO₃(s)+5H₂O(g) C) MgCO₃ · 5H₂O(s) → MgCO₃(s)+H₂O(g) D) MgCO₃ · 5H₂O(s) → MgCO₃(s)+5H₂O(g)
B) MgCO₃ · 5H₂O(s) → MgCO₃(s)+5H₂O(g)
In the event you need to write on your chromatogram, which should you use? Ron asks if he can use his finger... this is not acceptable. A) Pen B) Pencil C) Marker D) Paintbrush
B) Pencil
Review of Significant Figures: How many significant figures does the result of the following calculation have: 24.78*(37.3-31.72)? A) One significant figure B) Two significant figures C) Three significant figures D) Four significant figures
B) Two significant figures
What is the ability for a liquid to flow in a narrow channel or narrow tube often against gravity, without the assistance of external forces. A) viscosity B) capillary action C) deliquescence D) spectroscopy E) Tyndall effect
B) capillary action
Albus Dumbledore is a strict headmaster. He, like your professor in this course, requires you to answer all questions with the proper number of significant figures. To test your knowledge, what is the answer to the following problem, reported to the correct number of significant figures? 9.072 − 8.7497 -------------- 21.75 ∗ 0.09764 A. 0.15 B. 0.152 C. 0.1518 D. 0.15183 E. 0.151835
B. 0.152
Not being so pleased with the results, as he always is, Snape thinks it's best to give his students a similar problem. Which answer represents the correct chemical formulas for ammonium phosphate, barium chromate, and cesium sulfite. A. (NH₄)₂PO₃, BaCrO₃, Cs₂SO₄ B. (NH₄)₂PO₃, Ba₂CrO₃, CsSO₄ C. (NH₄)₃PO₄, BaCrO₄, Cs₂SO₃ D. (NH₄)₃PO₄, Ba₂CrO₃, CsSO₃ E. (NH₄)₂PO₄, BaCrO₃, Cs₂SO₃
C. (NH₄)₃PO₄, BaCrO₄, Cs₂SO₃
Severus Snape thinks it's important to understand the fundamentals. He would like to know the SI units for volume. What are they? A. L B. mL C. m³ D. gal E. ft³
C. m³
Hermione Granger is a diligent student. She wants to know what the empirical formula for C₄H₁₀ is. What is it? A) C₄H₄ B) CH₂ C) CH D) C₂H₅ E) C₂H₂
D) C₂H₅
Severus Snape explains that if you have the molar mass of a compound and the empirical formula of a compound you can determine the molecular formula of a compound. Suppose you have a compound which has an empirical formula of C₂H₃O and molar mass of 86 g/mol. What is the compounds molecular formula? A) C₂H₄O B) C₂H₅O C) C₂H₃O D) C₄H₆O₂ E) C6H₉O₃
D) C₄H₆O₂
Albus Dumbledore provides his students with a sample of 19.3 g of sodium sulfate. How many oxygen atoms are in this sample? A) 1.24*10²³ O atoms B) 4.97*10²³ O atoms C) 2.41*10²⁴ O atoms D) 3.27*10²³ O atoms E) 1.17*10²⁵ O atoms
D) 3.27*10²³ O atoms
Not only does Snape need to teach his students about hydration states, but also naming hydrates. What is the correct formula for barium hydroxide octahydrate and magnesium sulfate heptahydrate. A) BaOH · 8H₂O and MgSO₄ ·6H₂O B) Ba(OH)₂ · 8H₂O and Mg₂SO₄ ·6H₂O C) Ba(OH)₂ · 8H₂O and MgSO₄ ·6H₂O D) Ba(OH)₂ · 8H₂O and MgSO₄ ·7H₂O E) BaOH · 8H₂O and MgSO₄ ·7H₂O
D) Ba(OH)₂ · 8H₂O and MgSO₄ ·7H₂O
Great, now we can name compounds, let's start making solutions. Currently Severus is only using water as a solvent and thus can use only water soluble compounds. Which of the following can't Severus use? That is, which one of the following is insoluble in water. A) NaC₂H₃O₂ B) NH₄Br C) NH₄NO₃ D) BaSO₄ E) KCl
D) BaSO₄
What are the correct formulas for copper(II) nitrate hexahydrate and lithium chromate dihydrate? A) CuNO₃·6H₂O and Li₂CrO₄·2H₂O B) Cu(NO₃)₂·6H₂O and LiCrO₄·2H₂O C) Cu(NO₄)₂·6H₂O and LiCrO₄·2H₂O D) Cu(NO₃)₂·6H₂O and Li2CrO₄·2H₂O
D) Cu(NO₃)₂·6H₂O and Li2CrO₄·2H₂O
As you saw in problem 9 we can have species bound to a central metal ion. These species are called ligands. In the past we have assumed all the d orbitals in some species are degenerate; however, they often are not. Sometimes the ligands bound to a central metal cation can split the d orbitals. That is, some of the d orbitals will be at a lower energy state than others. Ligands that have the ability to cause this splitting are called strong field ligands, CN⁻ is an example of these. If this splitting in the d orbitals is great enough electrons will fill low lying orbitals, pairing with other electrons in a given orbital, before filling higher energy orbitals. In question 7 we had Fe²⁺, furthermore we found that there were a certain number (non-zero) of unpaired electrons. Consider now Fe(CN)₆⁴⁻: here we also have Fe²⁺, but in this case all the electrons are paired, yielding a diamagnetic species. How can you explain this? A) All the d orbitals are degenerate. B) There is 1 low lying d orbital, which will be filled with two electrons before filling the 4, assumed to be degenerate, higher energy orbitals. C) There are 2 low lying d orbitals, which will be filled with 4 electrons before filling the 3, assumed to be degenerate, higher energy orbitals. D) There are 3 low lying d orbitals, which will be filled with 6 electrons before filling the 2, assumed to be degenerate, higher energy orbitals. E) There are 4 low lying d orbitals, which will be filled with 8 electrons before filling the 1 higher energy orbital.
D) There are 3 low lying d orbitals, which will be filled with 6 electrons before filling the 2, assumed to be degenerate, higher energy orbitals.
Harry wants to know if there are any applications of chromatography. Gel elec- trophoresis is such an example. Gel electrophoresis is an example of which type of chromatography? A) Column chromatography B) Gas chromatography C) Paper chromatography D) Thin-layer chromatography
D) Thin-layer chromatography
Oh no... not again... Prof. Vitarelli spots Sybil running down the hall... yelling something... something about her tea cups... Prof. Vitarelli and Prof. Snape try to hold her back. But they fail. She yells, I've learned another exam question from last year! Zinc metal reacts with hydrochloric acid to produce hydrogen gas and an aqueous solution of zinc(II) chloride. What is the reducing agent in this reaction? Maybe Prof. Umbridge was right in trying to remove her. A) H₂ (g) B) ZnCl₂ (aq) C) HCl(aq) D) Zn(s)
D) Zn(s)
Which of the following, when dissolved in water, forms a weak acid. A. HNO₃ B. HClO₄ C. HBr D. HClO E. NH₃
D. HClO
Which combination of name and formula is NOT correct. A. Perchloric acid, HClO₄(aq) B. Potassium peroxide, K₂O₂(s) C. Barium hydroxide, Ba(OH)₂(aq) D. Iodic acid, HI(aq) E. Phosphoric acid, H₃PO₄(aq)
D. Iodic acid, HI(aq)
Which combination of name and formula is NOT correct. A. Chlorous acid, HClO₂(aq) B. Nitrous acid, HNO₂(aq) C. Hydrofluoric acid, HF(aq) D. Perchloric acid, HClO₃(aq) E. Hydrocyanic acid, HCN(aq)
D. Perchloric acid, HClO₃(aq)
Which of the following cations would you expect to be diamagnetic? A. Cu²⁺ B. Zn⁺ C. Al²⁺ D. Ti⁴⁺ E. Fe²⁺
D. Ti⁴⁺