The value of K_w like other equilibrium constants is dependent on temperature. At 30°C the value of K_w is 1.471×10^–14. Calculate the concentration of H₃O⁺ and the pH of pure water at this temperature.

Which member of the halogen group has the lowest electron affinity?

Which one of the following statements about electronegativity is correct?

Calculate the effective nuclear charge of the valence electrons of Mg based on the following theoretical conditions:

• core electrons completely shield electrons from nuclear charge
• valence electrons do not shield one another

Select the correct answer for each of the following questions. Each question has only one correct answer.

a) Which of the following elements has the largest atomic radius? 

      Li              K              O                S

b) Which of the following elements has the highest value of first ionization energy?

      Li              K              O                S

c) Which of the following elements has the greatest metallic character?

      Li              K              O                S

d) Which of the following ions has the largest radius? 

      Li⁺            K⁺             O^2-            S^2-

e) Which of the following is the most electronegative element?

      Ba              Ca               S             Te

Based on the condensed electron configurations and Lewis electron-dot symbols, predict the ions formed from the following atoms and determine the formula of their compound.

Ba and O

Identify the bond between each pair as ionic or covalent.

i) P and O
ii) Ba and S
iii) N and Br
iv) Cr and O

Identify what would happen to the dipole moment of HF if it is put under a great amount of pressure such that the bond lengths decrease significantly.

The octet rule applies to the elements of the main group but not to transition metals. Explain.

Shown below is the Lewis structure of bromate ion:

A. What is the formal charge on the bromine (Br) atom?

B. What is the formal charge of each of the oxygen (O) atoms labeled a, b, and c?

Formaldehyde is commonly used as an aqueous solution to preserve tissues and other samples from living organisms. The molecular formula for formaldehyde is CH₂O. Draw a Lewis structure for formaldehyde.

The potential energy of two atoms as a function of internuclear distance is shown in the diagram below. Identify the longer bond and the stronger bond.

Is azide ion (N₃⁻) and the triiodide ion (I₃⁻) isoelectronic?

PO₄³⁻ is a stable ion of phosphorous. Using Lewis structures, explain why NO₄³⁻ does not exist even though N and P are from the same group.

Draw the correct Lewis structure for HNO₃ that satisfies the octet rule

Which of the following can be done when transforming one resonance structure to another?

Is the C—C bond stronger between C₂H₄ or C₂H₆? Explain.

Estimate the ΔH°_rxn in kilojoules for the formation of methanethiol (CH₃SH) from methanol (CH₃OH):

CH₃OH(g) + H₂S(g) → CH₃SH(g) + H₂O(g)

Does increasing the distance between two electrons by 2.5 nm increase or decrease the potential energy?

The lattice energy of LiF is 1030 kJ/mol while that of KBr is 671 kJ/mol. Given that both LiF and KBr have the same rock salt structure and ionic charges, determine which compound have the greater ionic separation.

Calculate the lattice energy of NaBr.

A triple covalent bond is formed by the combination of:

Consider the compound SeOCl₄, which contains an O atom and four Cl atoms bonded to a central Se atom. Determine how many Cl atoms are equatorial and how many are axial in the molecule.

A theoretical molecule with the formula XY₃ has a T-shaped geometry. How many electron groups are on the central atom (X)?

Identify the molecular geometry of SF₄Cl₂.

Draw two structures with the formula C₃H₇N where there is at most one CH₃ group. Identify which structure would have a larger C-N-C bond angle.

Shown below is the structure of carbamic acid, a precursor in the industrial synthesis of urea. Use the VSEPR model to determine the hybridization and bond angles around the C and N atoms. Compare this with the actual hybridization and bond angles based on the 3D model below.

Legend: C = grey, H = white, O = red, N = blue

The last step in the formation of the hybrid orbitals of a carbon atom is illustrated in the orbital diagram below. Which of the following statements most accurately sums up what happened prior to the step depicted in the diagram?

(a) three electrons fill up the 2p atomic orbital

(b) the promotion of an electron into the 2p atomic orbital from the 2s orbital

(c) the 2s orbital becomes three orbitals