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UNSCO > UNSCO 2011 > Flashcards

UNSCO 2011 Flashcards

1
Q

Which solid does not react with a small amount of 3 M HNO3?

calcium carbonate
manganese(II) sulfide
potassium sulfite
silver chloride

A

silver chloride

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2
Q

A metal dissolves in dilute HCl in the absence of air to form a pale green solution that turns yellow upon exposure to air. The metal could be

iron.
manganese.
nickel.
vanadium.

A

iron.

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3
Q

Compounds of uranium-235 and uranium-238 can be separated from one another by

distillation.
effusion.
fractional crystallization.
paper chromatography.

A

effusion.

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4
Q
  1. A Material Safety Data Sheet (MSDS) provides what type(s) of information about a chemical?

I First aid measures II Handling and storage tips

I only
II only
Both I and II
Neither I nor II

A

Both I and II

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5
Q

When a 25.00 mL volumetric flask weighing 20.340 g is filled partially with metal shot the mass is 119.691 g. The flask is then filled to the 25.00 mL mark with methanol (d = 0.791 g•cm–3) and has a total mass of 130.410 g. What is the density of the metal?

  1. 96 g•cm–3
  2. 68 g•cm–3
  3. 27 g•cm–3
  4. 7 g•cm–3
A

8.68 g•cm–3

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6
Q

An aqueous solution contains the ions Ag+, Ba2+, and Ni2+. Dilute aqueous solutions of NaCl, Na2S, and Na2SO4 are available. In what order should these solutions be added if the goal is to precipitate each of the three cations separately?

Na2S, Na2SO4, NaCl
Na2S, NaCl, Na2SO4
Na2SO4, Na2S, NaCl
NaCl, Na2SO4, Na2S

A

NaCl, Na2SO4, Na2S

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7
Q

A 10.00 g sample of a compound containing C, H, and O is burned completely to produce 14.67 g of CO2 and 6.000 g of H2O. What is the empirical formula of this compound?

CHO
CH2O
CH2O2
C2H4O

A

CH2O

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8
Q

What is the molality of a solution made by dissolving 36.0 g of glucose (C6H12O6, M = 180.2) in 64.0 g of H2O?

  1. 0533
  2. 200
  3. 360
  4. 12
A

3.12

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9
Q

Which aqueous solution freezes at the lowest temperature?

  1. 30 m C2H5OH
  2. 25 m KNO3
  3. 20 m CaBr2
  4. 10 m FeCl3
A

0.20 m CaBr2

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10
Q

Element E reacts with oxygen to produce EO2. Identify element E if 16.5 g of it react with excess oxygen to form 26.1 g of EO2.

manganese
nickel
sulfur
titanium

A

manganese

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11
Q

Ethanol (C2H5OH, M = 46) and methanol (CH3OH, M = 32) form an ideal solution when mixed. What is the vapor pressure of a solution prepared by mixing equal masses of ethanol and methanol? (The vapor pressures of ethanol and methanol are 44.5 mm Hg and 88.7 mm Hg, respectively.)

133 mm Hg

  1. 6 mm Hg
    (66. 6 mm Hg
  2. 5 mm Hg
A

70.6 mm Hg (

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12
Q

A 5.00 L evacuated cylinder is charged with 25.5 g of NH3 and 36.5 g of HCl. Calculate the final pressure at 85.0 ˚C after the two compounds have reacted completely. NH3(g) + HCl(g) → NH4Cl(s)

  1. 94 atm
  2. 88 atm
  3. 82 atm
  4. 7 atm
A

2.94 atm

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13
Q

Pure samples of which of the following exhibit hydrogen bonding?

I CH3OH II CH3NO2 III CH3CN

I only
I and II only
II and III only
I, II, and III

A

I only

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14
Q

The average molecular velocity in a gas sample at 300 K is 500 m/s. The temperature of this gas is increased until the average velocity of its molecules is 1000 m/s. What is the new temperature?

420 K
573 K
600 K
1200K

A

1200K

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15
Q

Which of the following compounds has the lowest boiling point?

HF
HCl
HBr
HI

A

HCl

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16
Q

What is the coordination number of each atom in a hexagonal close-packed solid?

4
6
8
12

A

12

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17
Q

Spontaneous reactions always

go to completion.

are fast.

involve phase changes.

release energy and/or show an increase in the system’s entropy.

A

release energy and/or show an increase in the system’s entropy.

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18
Q

The standard enthalpies of combustion of formaldehyde, H2C=O(g),

and formic acid, HCOOH(l), are –563 and –270 kJ•mol–1 respectively. What is ∆H˚ for the following reaction?

H2C=O(g) + 1/2 O2(g) → HCOOH(l)

–833 kJ•mol–1
–293 kJ•mol–1
293 kJ•mol–1
833 kJ•mol–1

A

–293 kJ•mol–1

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19
Q

For Br2, ∆H˚vap = 31 kJ•mol–1. If S˚ values for Br2(g) and Br2(l) are 245 J•mol–1•K–1 and 153 J•mol-1•K–1 respectively, what is the normal boiling point for Br2(l)?

340 K
200 K
130 K
70 K

A

340 K

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20
Q

When MgO reacts with H2O at 25 ˚C and 1 atm, the volume change is –4.6 mL•mol–1. MgO(s) + H2O(l) → Mg(OH)2(s) What is the value of ∆H - ∆E for this reaction?

–4.7 × 10–1 J•mol–1
–4.7 × 102 J•mol–1
4.7 × 102 J•mol–1
4.7 × 10–1 J•mol–1

A

–4.7 × 10–1 J•mol–1

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21
Q

–For the dissolution of Ag2SO4, ∆H˚ = 17.8 kJ•mol–1 and ∆S˚ = –34.9 J•mol–1•K–1 at 25 ˚C.

What is the value of the Ksp for Ag2SO4 at this temperature?

  1. 0 × 10–2
  2. 6 × 10–4
  3. 3 × 10–4
  4. 1 × 10–5
A

1.1 × 10–5

22
Q

A rigid container holds an equal number of moles of N2 and H2 gas at a total pressure of 10.0 atm. The gases react according to the equation, N2(g) + 3 H2(g) 2 NH3(g). If the total pressure of the gas decreases at a rate of 0.20 atm•s–1, what is the rate of change of the partial pressure of N2 in the container?

decreases at 0.40 atm•s–1
decreases at 0.30 atm•s–1
decreases at 0.20 atm•s–1
decreases at 0.10 atm•s–1

A

decreases at 0.10 atm•s–1

23
Q

Consider the reaction, 2 NO(g) + Cl2(g) → 2 NOCl. Which of the following is/are required for a successful reaction between NO and Cl2 molecules?

I Proper orientation
II NO/Cl2 Ratio of 2 to 1
III Sufficient collision energy

II only
I and III only
II and III only
I, II, and III

A

I and III only

24
Q

When sucrose, C12H22O11, is dissolved in H2O in the presence of an acid catalyst it reacts according to the equation C12H22O11 + H2O → 2 C6H12O6 with a rate law of Rate = k[C12H22O11].

If 3.00 g of sucrose decreases to 2.70 g in 2.50 hours in the presence of a certain concentration of an acid catalyst, what is the half-life for this reaction under these same conditions?

  1. 5 hours
  2. 4 hours
  3. 7 hours
  4. 9 hours
A

16.4 hours

25
Q

For the reaction H2(g) + 2 ICl(g) → 2 HCl(g) + I2(g) one proposed mechanism is

H2(g) + ICl(g) → HICl(g) + H(g) slow
H(g) + ICl(g) → HCl(g) + I(g) fast
HICl(g) → HCl(g) + I(g) fast
I(g) + I(g) → I2(g) fast

Intermediates in this reaction include which of the following?

HICl only
I only
HICl and H only
HICl, H, and I

A

HICl, H, and I

26
Q

For the hypothetical reaction: A + B → C + D, the equilibrium constant, K, is less than 1.0 at 25 ˚C and decreases by 35% on changing the temperature to 45 ˚C. What must be true according to this information?

The ∆H˚ for the reaction is negative.
The ∆S˚ for the reaction is positive.
The ∆G˚ for the reaction at 25˚ is negative.
The ∆G˚ for the reaction at 45˚ is zero.

A

The ∆H˚ for the reaction is negative

27
Q

Consider the reaction carried out at constant volume: 2 SO2(g) + O2(g) 2 SO3(g).
For initial concentrations of SO2 and O2 of 2.0 M and 1.5 M, respectively, the equilibrium O2 concentration is 0.80 M. What is the value of Kc for this reaction?

  1. 8
  2. 9
  3. 34
  4. 15
A

6.8

28
Q

Correct statements about the percentage ionization of weak acids in water include which of the following?

I The percentage ionization increases as the ionization constant of the acid becomes larger.
II The percentage ionization increases as the concentration of the acid becomes smaller.

I only
II only
Both I and II
Neither I nor II

A

Both I and II

29
Q

What is the pH of the solution made by mixing 25.0 mL of 1.00 × 10–3 M HNO3 and 25.0 mL of 1.00 × 10–3 M NH3? [Kb for NH3 = 1.8 × 10–5]

  1. 02
  2. 28
  3. 72
  4. 98
A

6.28

30
Q

For the synthesis of ammonia, Kc is 1.2 at 375 ˚C N2(g) + 3 H2(g) 2 NH3(g), What is Kp at this temperature?

  1. 1 × 10–8
  2. 2 × 10–4
  3. 3 × 10–3
  4. 4 × 103
A

4.2 × 10–4

31
Q

Calculate the aqueous solubility of Ca(OH)2 in grams per liter. [Ksp = 8.0 × 10–6]

  1. 9 × 10–4
  2. 0 × 10–2
  3. 93
  4. 5
A

0.93

32
Q

What is the coefficient for Zn when the equation below is balanced with the smallest whole number coefficients?

Zn + H+(aq) + NO3– (aq) → Zn2+ (aq) + N2O(g) + H2O(l)

2
4
6
8

A

4

33
Q

For the reaction: C3H8(g) + 5 O2(g) → 3 CO2(g) + 4 H2O(l), ∆G˚ = –2.108 × 103 kJ•mol–1. What is the value of the standard electrode potential, E˚ for a fuel cell based on this reaction?

  1. 09 V
  2. 18 V
  3. 37 V
  4. 8 V
A

1.09 V

34
Q

What occurs when an aqueous solution of Na2SO4 containing several drops of phenolphthalein is electrolyzed between Pt electrodes?

The colorless solution turns pink at the anode but remains colorless at the cathode.

The colorless solution turns pink at the cathode but remains colorless at the anode.

The pink solution becomes colorless at the anode but remains pink at the cathode.

The pink solution becomes colorless at the cathode but remains pink at the anode.

A

The colorless solution turns pink at the cathode but remains colorless at the anode.

35
Q

A current of 12 A is used to plate nickel from a Ni(NO3)2 solution. Both Ni(s) and H2(g) are produced at the cathode.
If the current efficiency with respect to the formation of Ni(s) is 62%, how many grams of nickel are plated on the cathode in 45 minutes?

0.10
6.1
9.9
12

A

6.1

36
Q

Calculate the cell potential, E, for a silver-silver chloride electrode immersed in 0.800 M KCl at 25 ˚C.

[Ag+ + e– → Ag, E˚ = 0.799 V; Ksp = 1.8 × 10–10]

  1. 37 V
  2. 80 V
  3. 57 V
  4. 23 V
A

0.23 V

37
Q

Which gas-phase atom in its ground state has exactly three unpaired electrons?

Sc
Fe
Co
Se

A

Co

38
Q

The first ionization energy of Na is 495.9 kJ•mol–1. What is the longest wavelength of light that could remove an electron from a Na atom?

  1. 41 × 10–7 m
  2. 41 × 10–4 m
  3. 14 m
  4. 14 × 103 m
A

2.41 × 10–7 m

39
Q

Which set of quantum numbers could represent an electron in a 5f orbital?

l = 4, ml = 2
l = 2, ml = –3
l = 3, ml = 4
l = 3, ml = 0

A

l = 3, ml = 0

40
Q

Which orbital possesses one angular node and one radial node?

2s
2p
3p
3d

A

3p

41
Q

The radius of which ion is closest to that of the Li+ ion?

Na+
Be2+
Mg2+
Al3+

A

Mg2+

42
Q

Of the atoms listed, which has the largest third ionization energy?

Ca
Mg
Al
Si

A

Mg

43
Q

When the molecules N2, N2O, and N2O4 are arranged in order of decreasing N – N bond length, which order is correct?

N2O4, N2O, N2
N2, N2O, N2O4
N2O, N2, N2O4
N2, N2O4, N2O

A

N2O4, N2O, N2

44
Q

For the reaction: 3 H2 + N2 → 2 NH3 ∆H˚ = –97 kJ•mol–1. The H2 and N2 bond energies are 436 and 941 kJ•mol–1, respectively. What is the bond energy of a single N–H bond in kJ•mol–1? (

246
359
391
782

A

391

45
Q

What is the geometry of the IBr2– ion?

linear
bent with a bond angle of about 90˚
bent with a bond angle of about 109˚
bent with a bond angle of about 120˚

A

linear

46
Q

How many isomers exist for the [Co(NH3)4Cl2]+ and [Co(en)2Cl2]+ ions, respectively? [en = H2NC2H4NH2]

2 and 2
2 and 3
3 and 2
3 and 3

A

2 and 3

47
Q

Which statement best describes the structure of the allene molecule, H2C=C=CH2?

The C atoms form an angle of 120˚ and the H atoms lie in the same plane as the C atoms.

The C atoms form an angle of 120˚ and the H atoms lie in a plane perpendicular to that of the C atoms.

The C atoms form an angle of 180˚ and the four H atoms lie in the same plane.

The C atoms form an angle of 180˚ and the two CH2 groups are perpendicular to one another.

A

The C atoms form an angle of 180˚ and the two CH2 groups are perpendicular to one another.

48
Q

Oxidation of a secondary alcohol with K2Cr2O7 in sulfuric acid gives a product with which functional group?

aldehyde
carboxylic acid
ester
ketone

A

ketone

49
Q

What is the major product when nitrobenzene is treated with a mixture of HNO3 and H2SO4?

1,1-dinitrobenzene
,2-dinitrobenzene
1,3-dinitrobenzene
1,4-dinitrobenzene

A

1,3-dinitrobenzene

50
Q

Polysaccharides are biochemical molecules that consist of polymers of monosaccharide molecules (simple sugars). All of the following are classified as polysaccharides EXCEPT

cellulose.
fructose.
glycogen.
starch.

A

fructose.

51
Q

Which metal is found in vitamin B12?

Co
Cu
Fe
Mn

A

Co

52
Q

END

A

END

UNSCO (9 decks)

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