Question 1

Which of the following statements best describes the octet rule as it applies to main-group elements in organic molecules?

Accepted Answer

Atoms tend to combine so that each atom has eight electrons in its valence shell, similar to a noble gas.

Question 2

Which element does NOT always follow the octet rule in organic and biochemical molecules?

Accepted Answer

Phosphorus

Question 3

What is the correct Lewis structure for methane ($$CH_4$$)?

Accepted Answer

A central carbon atom with four single bonds to four hydrogen atoms, and no lone pairs on carbon.

Question 4

Which of the following best explains why the $$O-H$$ bond in water is polar?

Accepted Answer

Oxygen is more electronegative than hydrogen, so the shared electrons are pulled closer to oxygen.

Question 5

Given the following electronegativity values: $$C = 2.5$$, $$H = 2.1$$, $$O = 3.5$$, which bond is the most polar?

Accepted Answer

$$O-H$$

Question 6

Which of the following molecules has a bent molecular geometry according to VSEPR theory?

Accepted Answer

Water ($$H_2O)$$

Question 7

What is the approximate bond angle in ammonia ($$NH_3) $$due to the presence of a lone pair on nitrogen?

Accepted Answer

$$107^	ext{o}$$

Question 8

Which of the following best describes a nucleophilic attack in organic chemistry?

Accepted Answer

A reaction where an electron-rich species donates a pair of electrons to an electron-poor atom to form a new bond.

Question 9

Which of the following functional groups is present in both acetic acid ($$CH_3COOH) $$and glycine ($$NH_2CH_2COOH$$)?

Accepted Answer

Carboxylic acid group ($$-COOH)$$

Question 10

Which of the following statements about electronegativity is TRUE?

Accepted Answer

Electronegativity increases as you move up and to the right on the periodic table.

Question 11

A bond between two atoms has a difference in electronegativity ($$\Delta EN) of 2.0. $$What type of bond is this most likely to be?

Accepted Answer

Ionic bond

Question 12

Which of the following best describes the electron density in a non-polar covalent bond?

Accepted Answer

The electron density is evenly distributed between the two atoms.

Question 13

Which of the following is the correct Lewis structure for water ($$H_2O$$)?

Accepted Answer

An oxygen atom with two single bonds to hydrogen atoms and two lone pairs on oxygen.

Question 14

Which of the following best explains why lone pairs on central atoms affect molecular geometry?

Accepted Answer

Lone pairs occupy more space than bonding pairs, causing bond angles to decrease.

Question 15

Which of the following best describes the geometry and bond angle of methane ($$CH_4$$)?

Accepted Answer

Tetrahedral geometry with bond angles of $$109.5^	ext{o}$$

Question 16

Which of the following is a correct statement about the relationship between functional groups and chemical reactivity?

Accepted Answer

Functional groups determine the types of chemical reactions a molecule can undergo.

Question 17

A student is asked to draw the Lewis structure for ammonia ($$NH_3). $$Which of the following is correct?

Accepted Answer

A nitrogen atom with three single bonds to hydrogen atoms and one lone pair on nitrogen.

Question 18

Which of the following best describes the bond type in a $$C-H$$ bond?

Accepted Answer

Non-polar covalent bond

Question 19

Which of the following is a correct application of the VSEPR theory?

Accepted Answer

Electron pairs around a central atom arrange themselves as far apart as possible to minimize repulsion.

Question 20

A molecule has two areas of electron density around its central atom. According to VSEPR theory, what is its molecular geometry and bond angle?

Accepted Answer

Linear geometry with a bond angle of $$180^	ext{o}$$

Foundations of Organic Structure and Reactivity: GOB Chemistry Study Notes

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