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UNSCO > UNSCO 2009 > Flashcards

UNSCO 2009 Flashcards

1
Q

Which oxide produces an acidic solution when mixed with water?

Al2O3
CaO
CO
SO2

A

SO2

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2
Q

Which gas should not be collected over water due to its high solubility in water?

H2
N2
NH3
CH4

A

NH3

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3
Q

Which procedure(s) will allow a student to differentiate between solid sodium sulfate and solid sodium sulfite?

I. Make solutions of each and look for a precipitate when added to 0.10 M Ba(NO3)2.

II. Add crystals of each to 0.10 M HCl and watch for bubbles.

III. Make solutions of each and test with a pH indicator.

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

A

II and III only

III. Make solutions of each and test with a pH indicator.

I. Make solutions of each and look for a precipitate when added to 0.10 M Ba(NO3)2.

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4
Q

A student gets fingerprints on a cuvette before using it to determine the concentration of a colored species using its known extinction coefficient. What is the effect on the absorbance and reported concentration? absorbance reported concentration

increased too low
increased too high
decreased too low
decreased too high

A

increased too high

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5
Q

What color does the strontium ion produce in a flame test?

red
blue
green
yellow

A

red

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6
Q

What is the mass percent

UO2(C2H3O2) 2.NH4C2H3O2.6H2O 573

of oxygen in the compound UO2(C2H3O2)
2·NH4C2H3O2·6H2O?

  1. 58%
  2. 8%
  3. 3%
  4. 1%
A

39.1%

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7
Q

Reductic acid contains 52.63% carbon, 5.30% hydrogen, and 42.07% oxygen. Its empirical formula is the same as its molecular formula. What is the number of carbon atoms in a molecule of this acid?

4
5
6
8

A

5

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8
Q

Sulfur trioxide, SO3, is made by oxidizing sulfur dioxide, SO2, according to the equation, 2SO2 + O2 r 2SO3. If a 16.0 g sample of SO2 yields 18.0 g of SO3, what is the percent yield?

  1. 0%
  2. 0%
  3. 0%
  4. %
A

90.0%

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9
Q

A 1.0 g sample of which substance contains the largest number of molecules?

HN3
N2H4
H2O2
HCl

A

N2H4

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10
Q

What is the maximum m ass of PbI2 that can be
PbI2 461 precipitated by mixing 25.0 mL of 0.100 M Pb(NO3)2 with 35.0 mL of 0.100 M NaI?

  1. 807 g
  2. 15 g
  3. 61 g
  4. 30 g
A

0.807 g

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11
Q

Which statement is not a principle (postulate) of kinetic molecular theory?

The molecules of a gas are in rapid random motion.

The molecules of an ideal gas exhibit no attractive forces.

The collisions of gaseous molecules with one another and the walls of their container are elastic.

Equal volumes of gases at the same temperature and pressure contain equal numbers of molecules.

A

Equal volumes of gases at the same temperature and pressure contain equal numbers of molecules.

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12
Q

When a sample of an ideal gas is heated from 25˚C to 50˚C the average kinetic energy of the molecules increases. Which ratio gives the correct relationship between the average kinetic energies at the higher temperature to the lower temperature?

2 : 1
SQ ROOT 2: 1
323 : 298
SQ R OOT 323 : 298

A

323 : 298

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13
Q

A partially filled tank of propane contains both a liquid and a gas phase. Which of these statements about the contents of the two phases are correct?

I. The two phases have the same potential energy but different kinetic energies.
II. The two phases have the same molar masses but different densities.

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

A

II only

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14
Q

I. electrical conductivity
II. malleability

Which property or properties of metals can be accounted for by the electron sea model?

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

A

Both I and II

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15
Q

In a crystal of a typical metallic element, an atom has how many nearest neighbors?

4
6
12
16

A

12

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16
Q

Which aqueous solution has the highest osmotic pressure at 25˚C? (Assume all ionic compounds ionize completely in solution.)

  1. 1 M Al2(SO4)3
  2. 1 M Na2CO3
  3. 2 M KMnO4
  4. 3 M C6H12O6
A

0.1 M Al2(SO4)3

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17
Q

Which statement is correct at 25˚C and 1 atm pressure?

∆G˚f for Hg(l) = 0 kJ.mol–1
∆H˚f for I2(g) = 0 kJ.mol–1
∆H˚f for H2O(l) = 0 kJ.mol–1
S˚ for O2(g) = 0 J.mol–1.K–

A

∆G˚f for Hg(l) = 0 kJ.mol–1

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18
Q

What is the relationship among the magnitudes of the enthalpies of combustion (∆Hcomb), fusion (∆Hfus) and vaporization (∆Hvap) for a hydrocarbon such as hexane, C6H14?

∆Hfus < ∆Hcomb < ∆Hvap
∆Hvap < ∆Hfus < ∆Hcomb
∆Hcomb < ∆Hvap < ∆Hfus
∆Hfus < ∆Hvap < ∆Hcomb

A

∆Hfus < ∆Hvap < ∆Hcomb

19
Q

Which choice represents the signs for ∆S and ∆H for the sublimation of a compound that is occurring at constant temperature?

∆S < 0, ∆H < 0
∆S < 0, ∆H > 0
∆S > 0, ∆H > 0
∆S > 0, ∆H < 0

A

∆S > 0, ∆H > 0

20
Q

The enthalpy of fusion for NaF(s) at its melting point (992˚C) is 29.3 kJ.mol-1. What is the value of ∆Sfus˚ in J.mol-1.K-1?

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

23.2

21
Q

For the reaction at 25˚C, C2H4(g) + H2(g) s C2H6(g) Kp = 5.67×107 What is ∆G˚ for this reaction in kJ.mol-1?

–0.436
–3.71
–19.2
–44.2

A

–44.2

22
Q

For the irreversible reaction; A r B, which graph gives a straight line for a reaction that is second order in A? (A) [A] vs. time (B) 1 / [A] vs. time (C) [A]2 vs. time (D) 1 / [A]2 vs. time

A

1 / [A] vs. time

23
Q

A sample of a radioactive element that contains 1.0×103 nuclei decays to 6.2×101 nuclei in 10. minutes. What is its specific decay constant? (A) 6.2 min–1 (B) 1.2 min–1 (C) 0.28 min–1 (D) 0.062 min–1

A

0.28 min–1

24
Q

the oxidation of SO2 to H2SO4 in acid rain is thought to occur by the following mechanism. SO2(aq) + 2H2O(l) r HSO3–(aq) + H3O+(aq) 2HSO3–(aq) + O2(aq) r S2O72–(aq) + H2O(l) S2O72–(aq) + 3H2O(l) r 2SO42–(aq) + 2H3O+(aq) Which species in this mechanism can be given the following designations?

reactant catalyst intermediate

SO2(aq) H2O(l) HSO3–(aq), H3O+(aq)
SO2(aq) HSO3–(aq) S2O72–(aq)
SO2(aq), H2O(l) S2O72–(aq) HSO3–(aq)
SO2(aq), H2O(l) none HSO3–(aq), S2O72–(aq)

A

SO2(aq), H2O(l) none HSO3–(aq), S2O72–(aq)

25
Q

For the reaction; H2(g) + I2(g) r 2HI(g), the rate law is Rate = k[H2][I2]. Which of the mechanisms given is consistent with this rate law?

I. I2 s I + I (fast) H2 + I + I r 2HI (slow)
II. I2 s I + I (slow) H2 + I + I r 2HI (fast)

I only
II only
Either I or II
Neither I nor II

A

I only

26
Q 
The rate of a reaction at 100˚C is four times the rate at 50˚C. What is its activation energy? 
1152 kJ.mol-1  
80.1 kJ.mol-1
54.0 kJ.mol-1 
27.8 kJ.mol-1
A

27.8 kJ.mol-1

27
Q

The equilibrium system, N2O4(g) s 2NO2(g), has Kp = 11. For which equilibrium system is Kp = 0.091?

2NO2(g) s N2O4(g)
NO2(g) s 1 2N2O4(g)
2N2O4(g) s 4NO2(g)
1 2N2O4(g) s NO2(g)

A

2NO2(g) s N2O4(g)

28
Q

A 1.0 L evacuated tank is charged with HI(g) to a pressure of 1.0 atm at 793K. Some of the HI(g) forms H2 (g) and I2(g) according to the equilibrium; 2HI(g) s H2(g) + I2(g) Kp = 0.016 What is the pressure (in atm) of HI at equilibrium?

  1. 11
  2. 13
  3. 80
  4. 6
A

0.11

29
Q

A solution of 0.10 M NaZ has a pH = 8.90. What is the Ka of HZ?

  1. 6×10–4
  2. 6×10–5
  3. 3×10–10
  4. 3×10–11
A

6.3×10–10

30
Q

Which silver compound is the most soluble in water?

AgCl Ksp = 1.8×10-10
Ag2CO3 Ksp = 8.5×10-12
AgBr Ksp = 5.4×10-13
Ag3PO4 Ksp = 8.9×10-17

A

Ag3PO4 Ksp = 8.9×10-17

31
Q

When connected to a Standard Hydrogen Electrode (SHE) electrons flow from an unknown half cell to the SHE. Which statement is correct?

The unknown half cell is the anode.
Oxidation occurs at the SHE.
E˚red for the unknown half cell is positive.
E˚cell is negative.

A

E˚cell is negative.

32
Q

The cell Al(s) | Al3+(aq, 0.001 M) | | Cu2+(aq,0.10 M) | Cu(s) has a standard cell potential, E˚ = 2.00 V. What is the cell potential for this cell at the concentrations given?

  1. 07 V
  2. 03 V
  3. 97 V
  4. 94 V
A

2.03 V

33
Q

Ethanol reacts with dichromate ions in acid solution according to the equation;

C2H5OH(l) + Cr2O72–(aq) + H+(aq) r CO2(g) + Cr3+(aq) + H2O(l)

What is the coefficient for H+(aq) when this equation is balanced with the smallest whole number coefficients?

10
12
14
16

A

16

34
Q

Chromium metal can be produced by the electrolysis of molten CrO3. What current in amperes operating for 100 minutes is needed to produce 104 grams of this metal?

193

  1. 5
  2. 3
  3. 2
A

193

35
Q

What is the frequency of light with a wavelength of 480 nm?

  1. 60×10–6 s-1
  2. 25×105 s-1
  3. 25×1014 s-1
  4. 44×1020 s-1
A

6.25×1014 s-1

36
Q

Which set of quantum numbers (n,l, ml ) is forbidden?

3, 2, 0
3, 1, –1
2, 0, 0
1, 1, 0

A

1, 1, 0

37
Q

Which characteristic of an atomic orbital is most closely associated with the magnetic quantum number, ml?

size
shape
occupancy
orientation

A

orientation

38
Q

The energies of the 3s, 3p and 3d orbitals in a multielectron atom increase in that order. To which factor(s) can this order be attributed?

I. the relative penetrations of these orbitals near the nucleus
II. the relative average distance of the electron from the nucleus

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

A

I only

39
Q

Which element has the highest first ionization energy?

Al
Si
P
S

A

P

40
Q

Which species has a trigonal planar geometry?

ClF3
NCl3
CO32–
I3–

A

CO32–

41
Q

How many isomers exist for a square planar platinum compound which has four different groups attached to the platinum atom?

one
two
three
four

A

three

42
Q

The most notable difference between a saturated and an unsaturated fat containing the same number of carbon atoms is that the saturated fat

melts at a higher temperature.
melts at a lower temperature.
releases much more energy when metabolized.
releases much less energy when metabolized

A

melts at a higher temperature.

43
Q

END

A

END

UNSCO (9 decks)

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