Question 1

Which experiment provided the first evidence for the existence of electrons as subatomic particles?

Accepted Answer

Thomson's cathode ray tube experiment

Question 2

According to Bohr's model of the atom, which of the following statements is correct regarding electron transitions?

Accepted Answer

Electrons emit or absorb energy only when transitioning between quantized energy levels.

Question 3

Which quantum number determines the shape of an atomic orbital?

Accepted Answer

Azimuthal (angular momentum) quantum number ($$l)$$

Question 4

Which of the following best explains the trend in atomic radius across a period in the periodic table?

Accepted Answer

Atomic radius decreases due to increasing effective nuclear charge.

Question 5

A neutral atom has the electron configuration $$1s^2$$\ $$2s^2$$\ $$2p^6$$\ $$3s^2$$\ $$3p^5. $$Which element is this?

Accepted Answer

Chlorine ($$Cl)$$

Question 6

Which of the following molecules is nonpolar, despite having polar bonds?

Accepted Answer

Carbon dioxide ($$CO_2)$$

Question 7

Which statement best describes the difference between ionic and covalent bonds?

Accepted Answer

Ionic bonds involve transfer of electrons, while covalent bonds involve sharing of electrons.

Question 8

Which of the following best explains why sodium ($$Na) $$reacts vigorously with water, while magnesium ($$Mg) $$reacts much less vigorously?

Accepted Answer

Sodium loses its outer electron more easily due to its lower ionization energy.

Question 9

Which of the following sets of quantum numbers is NOT allowed for an electron in an atom?

Accepted Answer

$$n=2,\ l=2,\ m_l=0,\ m_s=+\frac{1}{2}$$

Question 10

Which of the following best describes the VSEPR (Valence Shell Electron Pair Repulsion) theory?

Accepted Answer

It explains the arrangement of atoms in a molecule based on repulsion between electron pairs.

Question 11

Which of the following elements has the highest electronegativity?

Accepted Answer

Fluorine ($$F)$$

Question 12

A sample of gas is collected in a laboratory at $$25^\circ C$$ and 1 atm. Which of the following equations correctly relates the pressure, volume, temperature, and number of moles for this gas?

Accepted Answer

$$PV = nRT$$

Question 13

Which of the following best explains why the ionization energy generally increases across a period?

Accepted Answer

The effective nuclear charge increases, holding electrons more tightly.

Question 14

Which of the following is a correct Lewis structure for the nitrate ion ($$NO_3$$^-$$)?

Accepted Answer

Nitrogen with one double bond and two single bonds to oxygen, with resonance among the oxygens.

Question 15

Which of the following best describes the dual nature of the electron?

Accepted Answer

Electrons exhibit both wave-like and particle-like properties.

Question 16

Which of the following is the best explanation for the shielding effect in atoms?

Accepted Answer

Inner electrons repel outer electrons, reducing the effective nuclear charge felt by the outer electrons.

Question 17

Which of the following compounds is expected to have the highest boiling point?

Accepted Answer

Water ($$H_2O)$$

Question 18

A chemist mixes solutions of silver nitrate ($$AgNO_3) $$and sodium chloride ($$NaCl). $$Which type of reaction occurs, and what is the precipitate formed?

Accepted Answer

Double displacement (precipitation); $$AgCl$$

Question 19

Which of the following statements about periodic trends is correct?

Accepted Answer

Ionization energy decreases down a group and increases across a period.

Question 20

Which of the following best describes the uncertainty principle?

Accepted Answer

It is impossible to know both the exact position and momentum of an electron simultaneously.

General Chemistry: Key Topics and Concepts (Course Syllabus Overview)

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