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Final Exam Flashcards

1
Q

Nitrogen tetroxide and hydrazine together can be used as rocket fuel. The products are only dinitrogen and water. What is the balanced equation for this reaction?

A

N2O4 + 2 N2H4 → 3 N2 + 4 H2O

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2
Q

What is the limiting reactant in the following reaction, if 75.0 g of zinc oxide and 50.0 g of carbon monoxide are used?

ZnO(s) + CO(g) → Zn(s) + CO2(g)
A

ZnO

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3
Q

Suppose you have a solution of two perfectly miscible liquids. Liquid A is the solvent, and liquid B is the solute. How can you change the solution so that liquid B becomes the solvent?

A

Add more of liquid B to the solution

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4
Q

Which of these aqueous solutions would most likely be the best conductor of electricity?

A

a 1.5 M solution of potassium chloride (KCl)

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5
Q

Heptane (C7H16 ) is insoluble in water. Which choice best explains why water is incapable of dissolving heptane (C7H16 )?

A

Heptane is a nonpolar molecule composed of a long hydrocarbon chain

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6
Q

The following reaction is of which type?

2KClO3(s) -> 2KCl(s) + 3O2(g)

A

oxidation-reduction reaction

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7
Q

What is the reduction half-reaction of the following equation?
2K(s) + 2H2O(l) -> 2K+(aq) + 2OH-(aq) + H2(g)

A

2H2O(l) + 2e- -> 2OH-(aq) + H2(g)

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8
Q

A 15.00 mL sample of unknown concentration of sulfuric acid is precititated with excess lead(II) nitrate and a precipitate of lead(II) sulfate is collected. The dried sample of PbSO4 has a mass of 5.354 grams. What is the concentration of the unknown sulfuric acid solution?

A

1.175 M

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9
Q

How many millilters of a 0.66 M solution of sodium dichromate would be needed to exactly titrate 55.1 mL of a 0.22 M solution of potassium iodide? The net ionic equation for the reaction in an acidic solution is:
Cr2O7(-2) + 6I(-) + 14H(+) –> 2Cr(3+)+3I2+7H2O

A

3.1 mL

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10
Q

The reaction of copper and silver nitrate is spontaneous.

Cu(s) + 2AgNO3(aq) →
Cu(NO3 )2(aq) + 2Ag(s)

The reverse reaction, in which silver metal is placed in the copper nitrate solution, is not spontaneous.

Which statement best describes the oxidizing and reducing abilities of the reactants?

A

Silver ion (Ag+ ) is a stronger oxidizing agent than copper ion (Cu2+ ) and copper metal is a stronger reducing agent than silver

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11
Q

A balloon containing 4.28 L of an unknown gas at 1.00 atm and 298 K has a mass of 16.90 g. The empty balloon has a mass of 2.24 g. What is the molar mass of the gas in the balloon?

A

83.8 g/mol

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12
Q

A 20.4 L tank at 298 K contains nitrogen gas with a partial pressure of 6.8 atm and helium gas with a partial pressure of 7.2 atm. What is the total pressure in the tank if the temperature is increased to 318 K?

A

14.9 atm

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13
Q

What type of reaction is shown by this graph?

A

exothermic

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14
Q

At a pressure of 1.00 atm, 10.5 calories of heat is added to a system, and the system expands against constant pressure from 2.0 L to 2.5 L. If ΔE = q + w = q − PΔV, what is the overall change in internal energy of the system?

A

ΔE = –6.8 J

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15
Q

A 3.57 g sample of cyclohexane (C6H12 ) is combusted in a bomb calorimeter. The temperature increases from 29.1°C to 31.3°C. What is the heat of the reaction for the combustion of this of cyclohexane in kilojoules per moles? The heat capacity of the calorimeter is 6.210 kJ/°C.

A

322 kJ / mol

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16
Q

Which of these correctly describes the relationship between ultraviolet light and visible light?

A

Ultraviolet light is electromagnetic radiation of higher frequencies and shorter wavelengths than visible light.

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17
Q

Which of these orbitals does not exist?

A

3f orbital

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18
Q

When filling multiple orbitals that have the same energy (called degenerate orbitals), two electrons are placed in different orbitals rather than paired in a single orbital. This is an example of which of the following?

A

Hund’s rule

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19
Q

As you move from the left to the right across the periodic table, which of the following is the trend?

A

Increasing ionization energy

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20
Q

A transition metal is defined as an element possessing partially filled d orbitals. When a transition metal is oxidized it first gives up electrons in the:

A

d orbital

21
Q

Which one of the following compounds would you expect to most be ionic?

A

Na2O

22
Q

Which of the following is the correct Lewis dot structure of the ethoxide anion, [CH3CH2O]−?

A

-7238

23
Q

Which of the following is required to form a bond in valence bond theory?

A

an unpaired electron on each atom

24
Q

Part of the first approach to assigning electrons in HF is shown in the diagram.

(The valence electrons have purposely not been included at this point.) Which statement about electron site assignments in HF is not true?

A

The bonding between the two atoms will occur between the 1s orbital of hydrogen and the 2s orbital of fluorine

25
Q

Generally speaking, which type of intermolecular attraction is the strongest?

A

dipole-dipole attraction

26
Q

Suppose a bottle of champagne has a partial pressure of 5.0 atm of CO2 above the liquid. Henry’s law constant (KH ) for CO2 in water at 25°C is 3.1 × 10−2 mol / L-atm. If we assume that champagne is essentially water, how much CO2 is dissolved in the liquid?

A

0.16 M

27
Q

When 3.00 g KNO3 are dissolved in 50 g glycerol, the freezing point changes from 17.8°C to 13.6°C. What is the freezing point depression constant (Kf ) for glycerol?

A

3.5 K/m

28
Q

Using the following data for the reaction 2NO2(g) + F2(g) → 2FNO2(g), what are the values of m, n, and k in the rate law rate = k[ NO2 ]m [ F2 ]n?

A

m = 1, n = 1, k = 24 M −1 • s−1

29
Q

The following reaction was observed in aqueous solution:

2Cu2+ (aq) + 6CN − (aq)
→ 2Cu(CN)2− (aq) + (CN)2(aq).

If the first step is the rapid development of Cu(CN)3− and the reaction rate was found to be k[Cu2+ ]2 [CN − ]6, what is the rate-determining step of this reaction?

A

2Cu(CN)3− (aq)

→ 2Cu(CN)2− (aq) + (CN)2(aq)

30
Q

In the following reaction,
CH4(g) + H2O(g) <==> CO(g) + 3H2(g)

assume that, initially, there is no methane. assume also that you have large amounts of the two products. which statement best summarizes the predicted movement of the reaction as it shifts towards equilibrium?

A

The reaction will move to the left because there initially is no methane

31
Q

What is the percent dissociation of a 0.20 M solution of the weak base methylamine? (NH2CH3 )?
(Kb = 4.4 × 10−4 )

A

4.7

32
Q

Consider the following reaction between nitrous acid and ammonia:
HNO2(aq) + NH3(aq) <==> NH4NO2(aq)
Ka = 4.510^-4
Kb = 1.810^-5
What is the equilibrium constant for this reaction?

A

8.1 × 10^5

33
Q

Suppose that you have a 68 mL solution of 0.12 M HCl that is being titrated with 0.12 M NaOH. Well before the equivalence point, you stop the titration. At this point, 38 mL of NaOH have been added. What is the change in pH at this point?

A

0.55

34
Q

What is the pH of the solution after 175 mL of 0.14 M H2(Ox) (oxalic acid) are titrated with 0.14 M NaOH (point I on the titration curve)?

A

8.5

35
Q

N2H4 and N2O4 are very high-energy molecules, while N2 and H2O are low-energy molecules. Based on this information, which of the following reactions is most likely to be spontaneous?

A

2N2H4 (l) + N204 (l) —-> 3N2(g) +4H20(l)

36
Q

Look at the fusion of water reaction.
H2O(l) <==> H2O(s)
At 273K, ΔH = -6,007 J/mol and ΔS = -22.0 J/mol*K. Suppose that we increase the temperature from 273 K to 283 K. Find the value for ΔG at 283 K and also tell whether the reaction is spontaneous at 283 K, nonspontaneous at 283 K, or at equilibrium

A

ΔG = 219 J / mol. The reaction is nonspontaneous at 283 K

37
Q

Which of the following is the properly balanced equation for the reaction of nitrous acid and iodide ion?
HNO2(aq) + I-(aq) -> NO(g) + I2(s)

A

2H+(aq) + 2HNO2(aq) + 2I-(aq) -> 2NO(g) + 2H2O(l) + I2(s)

38
Q

In the formation of rust in aerobic conditions, what is the role of the iron metal?

A

anode and conduit for electrons

39
Q

Which of the following correctly shows an alpha-emission reaction?

A

222 86 Rn -> 218 84 Po + 4 2 He

40
Q

You are given a worked wooden item from an archaeological dig believed to date to during the last glaciation. As such, the artifact would be another piece of evidence in favor of the hypothesis that North America was settled prior to the end of the last glaciation. You analyse the artifact and find that it has a specific activity of 2.2 dpm/g. How old is the artifact?

A

16,000 y

41
Q

Look at the 238 92 U reaction for a breeder reactor.

238 92 U + 1 0 n -> 239 93 Np + 0 -1 e -> 239 94 Pu + 0 -1 e

Which statement about this reaction is not correct?

A

This chain reaction has a total of two fissionable isotopes

42
Q

Which statement about fusion reactions is not correct?

A

Fission reactions are not currently being used as heat sources for fusion reactions

43
Q

A semiconductor is able to conduct a current:

A

in both the conduction band and the valence band.

44
Q

The Hall-Héraoult process for the electrolysis of aluminum oxide uses the mineral substance, cryolite (Na3AlF6 ), which of the following is not a reason for using cryolite?

A

The aluminum in cryolite serves a a nucleation site for the reduction reaction

45
Q

Which of the following is an unusual characteristic of interstitial hydrides?

A

Interstitial hydrides form in a non-stoichiometric relationship

46
Q

Coke, which is used in the purification of metal from metal oxides, is pure carbon. How does it differ from graphite, which is also pure carbon?

A

Coke is an amorphous solid, graphite is a crystalline solid

47
Q

What are the products of the commercially important decomposition of ammonium nitrate when heated?
NH4NO3(g) -> ? + ?

A

N2O(g) + 2H2O(g)

48
Q

Halogens tend to have high:

I. electronegativities
II. solublity in aqueous solution
III. ionization energies
IV. degrees of reactvity

A

I, II, III, and IV

49
Q

Which of the following noble gases has the lowest ionization energy?

A

xenon

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