Nursing Elites

1. Which of these types of intermolecular force is the strongest?

• A. Dipole-dipole interaction
• B. London dispersion force
• C. Keesom interaction
• D. Hydrogen bonding

Correct answer: D

Rationale: Hydrogen bonding is the strongest type of intermolecular force among the options provided. It occurs when a hydrogen atom is covalently bonded to a highly electronegative atom (such as nitrogen, oxygen, or fluorine) and forms a strong electrostatic attraction with an unshared pair of electrons on another electronegative atom. This type of bond is stronger than dipole-dipole interactions, London dispersion forces, and Keesom interactions due to the significant electronegativity difference between the hydrogen and the electronegative atom involved in the bond. The presence of hydrogen bonding contributes to unique properties in substances, such as high boiling and melting points, making it a crucial force in various biological and chemical processes.

2. What is the oxidation state of the nitrogen atom in the compound NH3?

• A. -3
• B. -1
• C. +1
• D. +3

Correct answer: B

Rationale: In the compound NH3, nitrogen is bonded to three hydrogen atoms. Hydrogen is always assigned an oxidation state of +1. Since the overall charge of NH3 is zero, the oxidation state of nitrogen must be -1 to balance out the hydrogen's +1 oxidation state. Therefore, the correct oxidation state of the nitrogen atom in NH3 is -1. Choice A (-3) is incorrect because it does not account for the electronegativity of hydrogen. Choice C (+1) and Choice D (+3) are incorrect as the nitrogen atom in NH3 needs to balance the +1 oxidation state of each hydrogen atom, resulting in a total of -3 to maintain the compound's charge neutrality.

3. What is the name of the device that separates gaseous ions by their mass-to-charge ratio?

• A. mass spectrometer
• B. interferometer
• C. magnetometer
• D. capacitance meter

Correct answer: A

Rationale: A mass spectrometer is a device specifically designed to separate gaseous ions based on their mass-to-charge ratio. This separation process involves ionization, acceleration of the sample, and the deflection of ions in a magnetic field according to their mass-to-charge ratio. The other options, 'interferometer,' 'magnetometer,' and 'capacitance meter,' do not perform the specific function of separating gaseous ions based on their mass-to-charge ratio, making them incorrect choices.

4. What color does phenolphthalein turn in the presence of an acid?

• A. Clear
• B. Blue
• C. Pink
• D. Red

Correct answer: C

Rationale: In the presence of an acid, phenolphthalein turns pink. Phenolphthalein is a pH indicator that is colorless in acidic solutions but turns pink in basic solutions. Therefore, when added to an acidic solution, phenolphthalein will exhibit a pink coloration. Choice A, 'Clear,' is incorrect because phenolphthalein does not remain colorless in the presence of an acid. Choice B, 'Blue,' is incorrect as phenolphthalein does not turn blue in the presence of an acid. Choice D, 'Red,' is incorrect as phenolphthalein does not exhibit a red color in acidic solutions.

5. If fifty-six kilograms of a radioactive substance has a half-life of 12 days, how many days will it take the substance to decay naturally to only 7 kilograms?

• A. 8
• B. 12
• C. 36
• D. 48

Correct answer: C

Rationale: To decay from 56 kg to 7 kg, the substance needs to go through 3 half-lives (56 kg ÷ 2 ÷ 2 ÷ 2 = 7 kg). Since each half-life is 12 days, the total time required is 12 days per half-life x 3 half-lives = 36 days. Choice A is incorrect because it does not consider the concept of half-lives. Choice B is incorrect because it represents the duration of a single half-life, not the total time required for the decay. Choice D is incorrect as it does not account for the multiple half-lives needed for the substance to decay from 56 kg to 7 kg.

Similar Questions