Compare the electron-dot formulas of $\text{BF}_{3}$ and $\text{NF}_{3}$. Why do these molecules have different shapes?

Predict the shape of a molecule with each of the following:

a. Two bonded atoms and no lone pairs

b. Three bonded atoms and one lone pair

Draw resonance structures for each of the following molecules or ions: a. $\mathrm{HCO}_2^{-}(\mathrm{C}$ is the central atom $)$ b. $\mathrm{N}_2 \mathrm{O}$

What is a discriminant in Maths?

Draw resonance structures for each of the following molecules or ions: a. $\mathrm{ClNO}_2$ ( $\mathrm{N}$ is the central atom) b. $\mathrm{OCN}^{-}(\mathrm{C}$ is the central atom)

Draw the electron-dot formula for each of the following molecules or ions: a. $\mathrm{HCCH}$ (ethyne) b. $\mathrm{CS}_2$ c. $\mathrm{NO}^{+}$

How many kilojoules are released when $75.0 \mathrm{~g}$ of steam at $100{ }^{\circ} \mathrm{C}$ condenses, cools to $0^{\circ} \mathrm{C}$, and freezes? (Hint: The solution will require three energy calculations.)

Draw the electron-dot formula for $\mathrm{Cl}_2 \mathrm{O}$.

Outline the structure and functions of cell walls, and explain the role of peptidoglycan.

Determine the total number of valence electrons for each of the following: a. $\mathrm{H}_2 \mathrm{~S}$ b. $\mathrm{I}_2$ c. $\mathrm{CCl}_4$ d. $\mathrm{OH}^{-}$

A $100-\mathrm{Hz}$ pure tone at a $70-\mathrm{dB}$ sound level and a $1,000-\mathrm{Hz}$ pure tone at the same sound level are heard separately. Do they sound equally loud? If not, which is louder, and why?

Compare the sequence of events in the mitotic cell cycle with the sequence of events in apoptosis.

Summarize how snowflakes and hail form, and how water molecules can move between water vapor, water drops, and snowflakes.

The rate of a reaction was followed by measuring the absorption of light by the reactants and products as a function of wavelength $\left(\lambda_1, \lambda_2, \lambda_3\right)$ as time progressed (see Figure on p. 771). Which of the following mechanisms is consistent with the experimental data? (a) $\mathrm{A} \longrightarrow \mathrm{B}, \mathrm{A} \longrightarrow \mathrm{C}$. (b) $\mathrm{A} \longrightarrow \mathrm{B}+\mathrm{C}$. (c) $\mathrm{A} \longrightarrow \mathrm{B}, \mathrm{B} \longrightarrow \mathrm{C}+\mathrm{D}$. (d) $\mathrm{A} \longrightarrow \mathrm{B}, \mathrm{B} \longrightarrow \mathrm{C}$.