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CHEMISTRY FINAL B > PART B > Flashcards

PART B Flashcards

1
Q

According to the Second Law of Thermodynamics, the entropy of the Universe always increases for a spontaneous process. Since entropy S = q/T, heat transfer always occurs from a body of higher temperature to a body of lower temperature because:

the entropic decrease for a hotter body is outweighed by the entropic increase for a colder body.

the entropic increase for a hotter body is outweighed by the entropic decrease for a colder body.

the entropic increase for a hotter body is outweighed by the entropic increase for a colder body.

the entropic decrease for a hotter body is outweighed by the entropic decrease for a colder body.

A

the entropic decrease for a hotter body is outweighed by the entropic increase for a colder body.

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2
Q

If 14.5 kJ of heat were added to 485 g of liquid water, how much would its temperature increase, given that the specific heat of water is 4.18 J.g-1.K-1?

280 oC

  1. 15 oC
  2. 9 oC

none of these

A

7.15 oC

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3
Q

A piece of unknown solid substance weighs 437.2 g, and requires 8460 J to increase its temperature from 19.3 °C to 68.9 °C. What is the specific heat of the substance?

2.56 J.g-1.℃-1

none of these

  1. 390 J.g-1.℃-1
  2. 390 J.g.℃-1
A

0.390 J.g-1.℃-1

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4
Q

Calculate the ΔH for the process:

Sb(s) + Cl2 (g) → SbCl5 (g)
From the following information:

Sb(s) + Cl2 (g) → SbCl3 (s) ΔH = -314 kJ
SbCl3 (s) + Cl2 (g) →SbCl5 (g) ΔH = -80 kJ

  • 394 kJ
  • 234 kJ

394 kJ

+234 kJ

A

-394 kJ

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5
Q

Calculate ΔH for the process:

Hg2Cl2 (s) → 2 Hg (l) + Cl2 (g)
from the following information:

Hg (l) + Cl2 (g) → HgCl2 (s) ΔH = -224 kJ
Hg (l) + HgCl2 (s) → Hg2Cl2 (s) ΔH = -41.2 kJ

  • 182.8 kJ
  • 265 kJ
    182. 8 kJ

265 kJ

A

265 kJ

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6
Q

Calculate the standard molar enthalpy of formation of NO(g) from the following data:

N2 (g) + 2 O2 (g) → 2 NO2 (g) ΔH = 66.4 kJ
2NO (g) + O2 (g) → 2 NO2 (g) ΔH = -114.1 kJ

Hint: be careful because you should calculate the formation for one mole only.

  • 180.5 kJ mol-1
    180. 5 kJ mol-1
    90. 3 kJ mol-1
  • 90.3 kJ mol-1
A

90.3 kJ mol-1

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7
Q

For the species, NaCl, CH4 and CO2, the bonds between the atoms/ions would be respectively:

ionic, polar covalent, non-polar covalent

ionic, non-polar covalent, polar covalent

polar covalent, non-polar covalent, ionic

polar covalent, ionic, non-polar covalent

A

ionic, non-polar covalent, polar covalent

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8
Q

Explain why the HOH molecule is bent, whereas the HBeH molecule is linear.

A

The oxygen in water has four pairs of electrons, two involved in bonding with hydrogen, the other two pairs in a non-bonding arrangment. According to VSEPR theory, these four pairs would tend to form a tetrahedral arrangement with bond angles of about 109 degrees to minimize repulsion between these electron pairs.

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9
Q

Explain how a molecule that contains polar bonds can be nonpolar.

A

As long as the polar bonds are compensated (for example. two identical atoms are found directly across the central atom from one another), the molecule can be nonpolar. For example, for carbon dioxide, the molecule is linear in accordance with VSEPR Theory: O=C=O this means that, although the C=O bonds are polar, because each oxygen pulls with the same amount of force in equal directions, the polarity is effectively cancelled, making the molecule non-polar overall

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10
Q

Which of the following molecules have net dipole moments?

a) CS2
(b) H2Se
(c) CCl2F2
(d) PCl3 (P is the central atom

A

(b), (c) and (d)

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11
Q

The bond angles between the central nitrogen and hydrogen in ammonium ion and ammonia would be respectively:

107o and 107o

107o and 109o

109o and 109o

109o and 107o

A

109o and 107o

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12
Q

The molecule XF3 has a dipole moment. Based on this information, X could be:

boron or phosphorus

boron, phosphorus or nitrogen

boron or nitrogen

nitrogen or phosphorus

A

nitrogen or phosphorus

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13
Q

A spray can is used until it is empty except for the propellant gas, which has a pressure of 1344 torr at 23 oC. If the can is thrown into a fire (T = 475 oC), what will be the pressure in the hot can?

  1. 40 x 103 torr
  2. 40 torr

1344 torr

none of these

A

3.40 x 103 torr

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14
Q

A 2.50 L volume of hydrogen measured at –196 oC is warmed to 100 oC. What is the volume of the gas at the higher temperature, assuming no change in pressure?

740 L

25 L

  1. 1 L
  2. 1 L
A

12.1 L

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15
Q

A weather balloon contains 8.80 moles of helium at a pressure of 0.992 atm and a temperature of 25 oC at ground level. What is the volume of the balloon under these conditions? The Ideal Gas Constant is 0.08206 L atm mol-1 K-1.

0.992 L

217 L

2170 L

100 L

A

217 L

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16
Q

A cylinder of medical oxygen has a volume of 35.4 L, and contains O2 at a pressure of 151 atm and a temperature of 25 oC. What volume of O2 does this correspond to at normal body conditions, that is, 1 atm and 37 °C?

5561 L

50 L

3540 L

1510 L

A

5561 L

17
Q

The intermolecular forces present in ethanol, CH3CH2OH would be:

permanent dipole-permanent dipole.

hydrogen bonding and dispersion forces.

hydrogen bonding and covalent bonds.

covalent only.

A

hydrogen bonding and dispersion forces.

18
Q

Consider this equation:

MnO4- + Fe2+ → Mn2+ + Fe3+
Which one of the following statements is true?

MnO4- is oxidised and Fe2+ is the oxidant.

MnO4- is oxidised and Fe2+ is the reductant.

MnO4- is reduced and Fe2+ is the oxidant.

MnO4- is reduced and Fe2+ is the reductant.

A

MnO4- is reduced and Fe2+ is the reductant

19
Q

Aluminium is a potent electron donor (reductant) and yet is used extensively in marine environments because of its resistance to corrosion. This is because:

aluminium is easily oxidised.

none of these

of passivation.

aluminium is easily reduced.

A

of passivation.

20
Q

Ethyl acetate has been used in the past as nail polish remover. It is synthesised from ethanol and acetic acid, both of which are easily obtained in microbial fermentation reactions. Ethyl acetate is classified as an _______ and its synthesis would be classified as a _____________ reaction.

ether, dehydrogenation

ester, dehydration

ether, dehydration

ester, dehydrogenation

A

ester, dehydration

21
Q

A peptide bond is a special form of ________ bond, formed by a _____________reaction between a ______________ acid and an ________ group

amide, dehydration, strong, amino

amide, dehydration, carboxylic, amide

amine, dehydration, carboxylic, amino

amide, dehydration, carboxylic, amino

A

amide, dehydration, carboxylic, amino

22
Q

A machine generates x-rays whose wavelength is 2.090 x 10-11 m. The energy of a photon and the frequency of the ray would be respectively:

  1. 502 x 10-15 J and 1.434 x 1019 s-1
  2. 502 x 10-15 s-1 and 1.434 x 1019 J

none of these

9.502 x 1015 J and 1.434 x 1019 s-1

A

9.502 x 10-15 J and 1.434 x 1019 s-1

23
Q

Which is/are isoelectronic with Br+?

Se and As

Ga3+

Cl- and Kr

Se and As-

A

Se and As-

24
Q

Lithium has a much lower ionization energy than hydrogen and is due to:

shielding and distance.

and increase in nuclear charge and distance.

a decrease in nuclear charge and distance.

shielding only.

A

shielding and distance.

25
Q

Nitrogen has a higher ionization energy than oxygen. This is because:

Nitrogen has three half-filled 2p orbitals.

Oxygen has three half-filled 2p orbitals.

Nitrogen has three half-filled 2s orbitals.

Oxygen has three half-filled 2p orbitals.

A

Nitrogen has three half-filled 2p orbitals.

26
Q

Catalysts act to increase the rate of a reaction by:

making the reactants more energetic.

increasing the kinetic energy of the reactants.

producing heat.

lowering the activation energy using an alternative reaction pathway.

A

lowering the activation energy using an alternative reaction pathway.

27
Q

You carry out a reaction of magnesium metal with a solution of hydrochloric acid. Which change to the following conditions will always increase the reaction rate?

Decrease the molarity of hydrochloric acid, increase the temperature, decrease the size of the pieces of magnesium.

Increase the molarity of hydrochloric acid, increase the temperature, increase the size of the pieces of magnesium.

Decrease the molarity of hydrochloric acid, decrease the temperature, decrease the size of the pieces of magnesium.

Increase the molarity of hydrochloric acid, increase the temperature, decrease the size of the pieces of magnesium.

A

Increase the molarity of hydrochloric acid, increase the temperature, decrease the size of the pieces of magnesium.

28
Q

Consider the following reaction:

N2 (g) + 2H2 (g) ↔ N2H4 (g) ∆H = 95 kJ/mole
Which of the following would cause an increase in the concentration of hydrazine (N2H4)?

add N2; add H2; decrease the container volume; heat the mixture

add N2; add H2; increase the container volume; heat the mixture

add N2; add H2; decrease the container volume; cool the mixture

decrease N2; add H2; decrease the container volume; heat the mixture

A

add N2; add H2; decrease the container volume; heat the mixture

29
Q

Kw is 2.9 × 10–14 at 40 oC. Therefore the [H3O+] in a sample of pure water at this temperature is:

7 x 10-7 M

1.7 x 10-7 M

1 x 10-7 M

2.9 × 10–14 M

A

1.7 x 10-7 M

30
Q

Kw is 2.9 × 10–14 at 40 oC. Therefore the pH in a sample of pure water at this temperature is:

  1. 9
  2. 7
  3. 8
  4. 0
A

6.8

31
Q

What is the pH of a buffer composed of 0.1 M acetic acid and 0.6 M acetate ion?

The Ka of acetic acid is 1.8 x 10-5.

7

6

  1. 7
  2. 48
A

5.48

32
Q

The main buffer system in the blood is carbonic acid (H2CO3)/hydrogen carbonate (HCO3-). The pKa of carbonic acid is 6.4. Given the concentrations of carbonic acid and hydrogen carbonate ion are respectively 0.0012 M and 0.024 M, what would be the pH of blood if only due to this buffer system?

  1. 4
  2. 0
  3. 4
  4. 7
A

7.7

33
Q

Kw is 2.9 × 10–14 at 40 oC. Therefore the pH in a sample of pure water at this temperature is:

  1. 0
  2. 7
  3. 9
  4. 8
A

6.8

34
Q

Kw is 2.9 × 10–14 at 40 oC. Therefore the [H3O+] in a sample of pure water at this temperature is:

2.9 × 10–14 M

7 x 10-7 M

1 x 10-7 M

1.7 x 10-7 M

A

1.7 x 10-7 M

35
Q

A 25 ml solution of 0.5 M NaOH is titrated until neutralized into a 50 ml sample of HCl. What was the molar concentration of HCl?

  1. 5 M
  2. 25 M

2 M

0.25 moles

A

0.25 M

CHEMISTRY FINAL B (1 decks)

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