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UNSCO > UNSCO 2014 > Flashcards

UNSCO 2014 Flashcards

1
Q

Boron carbide, B4C, is made by the high temperature reaction of boron oxide with graphite, yielding carbon monoxide as a by-product. __ B2O3 + __ C  __ B4C + __ CO What is the total of the smallest coefficients for the reactants and products in the balanced equation?

9
10
15
16

A

16

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2
Q

A compound with 69.41% C, 4.16% H and 26.42% O has a molar mass of 230 – 250 g•mol–1. What is its molecular formula?

C13H9O4
C14H10O4
C13H6O4
C15H14O3

A

C14H10O4

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3
Q

Aluminum reacts with sulfur to form aluminum sulfide. If 31.9 g of Al are reacted with 72.2 g of S, what is the theoretical yield of aluminum sulfide in grams?

88.8 g
69.7 g
57.2 g
113 g

A

88.8 g

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4
Q

According to EPA guidelines the permissible level for lead in drinking water is 15 parts per billion (ppb). What is the maximum allowable mass of lead that could be present in 1.00 L of H2O?

  1. 015 ng
  2. 015 µg
  3. 015 mg
  4. 015 g
A

0.015 mg

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5
Q

According to EPA guidelines the permissible level for lead in drinking water is 15 parts per billion (ppb). What is the maximum allowable mass of lead that could be present in 1.00 L of H2O?

  1. 015 ng
  2. 015 µg
  3. 015 mg
  4. 015 g
A

0.015 mg

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6
Q

Aqueous solutions of electrolytes that produce two ions upon ionization typically exhibit freezing point depressions that are twice as large as solutions of nonelectrolytes with the same concentration. Which 0.10 M electrolyte solution will show the smallest depression?

HCl
NaBr
KNO3
MgSO4

A

MgSO4

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7
Q

Interferon is a water-soluble protein. A solution prepared by dissolving 15.0 mg of interferon in 2.50 mL of H2O exhibits an osmotic pressure of 5.80 mm Hg at 25 °C. What is the molar mass of interferon?

  1. 92 × 104 g•mol–1
  2. 92 × 107 g•mol–1
  3. 95 × 106 g•mol–1
  4. 61 × 103 g•mol–1
A

1.92 × 104 g•mol–1

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8
Q

Which noble gas is most abundant in the earth’s atmosphere? (A) He (B) Ne (C) Ar (D) Rn

A

Ar

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9
Q

Which of the acids below has the most ionizable hydrogen atoms per molecule?
I. H3PO4 II. H3PO3 III. H3PO2

I only
II only
III only
Each one contains the same number of ionizable H atoms

A

I only

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10
Q

Aluminum is most often found in nature as the

carbonate
chloride.
oxide.
sulfide

A

oxide.

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11
Q

According to the Tyndall effect, a beam of light becomes visible when passed through all of the following except a(n)

aerosol.
colloid.
emulsion.
solution

A

solution.

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12
Q

All of the following can be used as primary standards in acid-base titrations EXCEPT

oxalic acid.
potassium hydrogen phthalate.
sodium carbonate
sodium hydroxide.

A

sodium hydroxide

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13
Q

Which physical property decreases with an increase in intermolecular molecular forces?

boiling point
enthalpy of vaporization
vapor pressure
viscosity

A

vapor pressure

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14
Q

A 0.180 g sample of liquid H2O is injected into a 5.00 L flask at 25 °C. What will be present in the flask when equilibrium is established? (Vapor pressure H2O at 25 °C = 23.8 mm Hg)

H2O vapor at a pressure of 186 mm Hg

H2O vapor at a pressure of 37.2 mm Hg

liquid H2O and H2O vapor at a pressure of 37.2 mm Hg

liquid H2O and H2O vapor at a pressure of 23.8 mm Hg

A

liquid H2O and H2O vapor at a pressure of 23.8 mm Hg

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15
Q

The atmospheric pressure on the summit of Mt. Everest is 0.333 atmospheres. At what temperature (in °C) does H2O boil there? (∆Hvap H2O = 40.7 kJ•mol–1)

71 °C
87 °C
96 °C
98 °C

A

71 °C

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16
Q

The arrangement of ions in a solid is best investigated by means of

infrared spectroscopy.
mass spectroscopy.
UV-visible spectroscopy.
x-ray crystallography.

A

x-ray crystallography.

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17
Q

Benzene and toluene form an ideal solution. The vapor pressure of benzene at 55 °C is 400 mm Hg while the vapor pressure of toluene at 55 °C is 130 mm Hg. What is the vapor pressure of a solution consisting of 0.5 mole fraction of benzene and 0.5 mole fraction of toluene at 55 °C?

lower than 130 mm Hg
between 130 and 400 mm Hg
exactly 400 mm Hg
greater than 400 mm Hg

A

between 130 and 400 mm Hg

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18
Q

An oxide of rhenium crystallizes with eight rhenium atoms at the corners of the unit cell and 12 oxygen atoms on the edges between them. What is the formula of this oxide?

ReO
Re2O3
ReO2
ReO3

A

ReO3

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19
Q

Which isomer of C4H8 has the lowest absolute entropy at 25 °C?

1-butene
cis-2-butene
trans-2-butene
cyclobutane

A

cyclobutane

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20
Q

In the Born-Haber calculation of the lattice enthalpy of LiF from its elements, which process is exothermic? (

dissociation energy of F2(g)
electron affinity of F(g)
ionization energy of Li(g)
sublimation energy of Li(s)

A

electron affinity of F(g)

21
Q

How much work is done by the gas when 1.00 g of sodium azide, NaN3 (M = 65.01 g•mol–1), decomposes in a container of changeable volume (e.g. an airbag in a car) against a constant pressure of 1.00 atm at 298 K?

2 NaN3(s)  2 Na(s) + 3 N2(g)

+114 J
+57.2 J
–114 J
–57.2 J

A

+57.2 J

22
Q

the reaction above, a straight line for which plot indicates a second order reaction?

[NO2] vs. time
[NO2]2 vs. time
1/[NO2] vs. time
1/[NO2]2 vs. time

A

1/[NO2] vs. time

23
Q

What are the units for the rate constant of a zero-order reaction?

time
time–1
M•time
•time–1

A

M•time–1

24
Q

The half-life of a first-order reaction is 1.5 hours. How much time is needed for 94% of the reactant to change to product?

0.13 hours
6.1 hours
2.3 hours
36 hours

A

6.1 hours

25
Q

A 50.0 mL sample of a 1.00 M solution of a diprotic acid H2A (Ka1 = 1.0 × 10–6 and Ka2 = 1.0 × 10–10) is titrated with 2.00 M NaOH. What is the minimum volume of 2.00 M NaOH needed to reach a pH of 10.00?

  1. 5 mL
  2. 5 mL
  3. 0 mL
  4. 0 mL
A

37.5 mL

26
Q

For the reaction, O2(g) + 2 F2(g) 2 OF2(g), Kp = 41.0. If PO2(g) = 0.116 atm and PF2(g) = 0.0461 atm at equilibrium, what is the pressure of OF2(g)?

0.101 atm
0.132 atm
0.760 atm
166 atm

A

0.101 atm

27
Q

For the reaction 2 HI(g) H2(g) + I2(g), what is the relationship between Kc and Kp at 25 °C?
Kc = Kp
Kc > Kp
Kc < Kp
The relationship varies depending on the pressure.

A

Kc = Kp

28
Q

Calcium hydroxide is slightly soluble in water with a Ksp of 1.3×10–6. What is the pH of a saturated solution of calcium hydroxide at 25 °C?

  1. 34
  2. 14
  3. 04
  4. 84
A

12.14

29
Q

For the reaction, ADP + phosphate  ATP, ∆G° = 30.50 kJ•mol–1. What is the value of the equilibrium constant, K, for this process under physiological conditions of 37.5 °C?

  1. 5 × 10–6
  2. 4 × 10–6
  3. 3 × 105
  4. 2 × 105
A

7.4 × 10–6

30
Q

When 0.0030 mol of HCl is added to 100. mL of a 0.10 M solution of a weak base, R2NH, the solution has a pH of 11.10. What is Kb for the weak base?

  1. 9 × 10–3
  2. 4 × 10–4
  3. 1 × 10–5
  4. 6 × 10–5
A

5.4 × 10–4

31
Q

The advantages of methane fuel cells over internal combustion engines (ICEs) that burn methane include which of the following? I. Methane fuel cells are less polluting. II. Methane fuel cells are more efficient. III. Methane fuel cells are less expensive.

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

A

I and II only

32
Q

A steady current of 1.20 Ampere is passed through a solution of MClx for 2 hours and 33 minutes. If 2.98 g of metal M are plated out, what is the identity of the metal?

Al
Cr
Ni
Zn

A

Cr

33
Q

How many angular nodes does a d orbital possess?

1
2
3
4

A

2

34
Q

For the transition metal with the electron configuration 1s22s22p63s23p64s23d6, how many unpaired electrons are present in its +2 ion in the ground state?

0
2
4
6

A

4

35
Q

What is the velocity of an electron (m = 9.11 × 10–28 g) that exhibits a de Broglie wavelength of 10.0 nm? [1 J = 1 kg•m2•s–2]

72.7 m•s–1
270 m•s–1 (
7.27 × 104 m•s–1
7.27 × 106 m•s–1

A

7.27 × 104 m•s–1

36
Q

Which atom has the highest first ionization energy?

Al
Si
P
S

A

P

37
Q

What are the two most common oxidation states for antimony?

–1 and –3
–1 and +2
+3 and –3
+3 and +5

A

+3 and +5

38
Q

For which pair of species are the radii most similar?

Li and Na
Na and Mg
Mn and Fe
Fe2+ and Fe3+

A

Mn and Fe

39
Q

When arranged in order of increasing bond strength, which order is correct?

O–O < S–S < O=O < S=S
O–O < S–S < S=S < O=O
S–S < O–O < O=O < S=S
S–S < O–O < S=S < O=O

A

O–O < S–S < S=S < O=O

40
Q

Molecules with a permanent dipole moment include which of the following?

I. HCN II. O3 III. XeF2

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

A

I and II only

41
Q

How many stable resonance forms can be written for the oxalate ion, C2O42–?

two
three
four
five

A

four

42
Q

What is the geometry of ICl4– according to VSEPR theory?

see-saw
square planar
tetrahedral
T-shaped

A

Square planar

43
Q

Mild oxidation of 1-propanol, CH3CH2CH2OH, leads to the formation of

propanal, CH3CH2CHO.
propanoic acid, CH3CH2COOH.
2-propanone, CH3COCH3.
dipropyl ether, CH3CH2CH2OCH2CH2CH3.

A

propanal, CH3CH2CHO.

44
Q

Which is the principal cation within cellular fluid?

Na+
K+
Mg2+
Ca2+

A

K+

45
Q

The shape of a chain segment of polypeptide chains in a protein is known as its

primary structure.
secondary structure.
tertiary structure.
quaternary structure

A

secondary structure.

46
Q

Which property that polyacetylene exhibits is unusual for an organic polymer?

electrical conductivity
flexibility
high boiling point
strength

A

electrical conductivity

47
Q

Which type of dietary fat is the least healthy for humans?

cis-monounsaturated fat
polyunsaturated fat
saturated fat
trans-monounsaturated fat

A

trans-monounsaturated fat

48
Q

END

A

END

UNSCO (9 decks)

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