AP Chemistry Review 2.4-2.7

To make Au stronger and harder, it is often alloyed with other metals, such as Cu and Ag. Consider two alloys, one of Au and Cu and one of Au and Ag, each with the same mole fraction of Au. If the Au/Cu alloy is harder than the Au/Ag alloy, then which of the following is the best explanation based on the information in the table above? (Topic 2.4)

• Cu has two common oxidation states, but Ag has only one.

• Cu has a higher melting point than Au has, but Ag has a lower melting point than Au has.

• Cu atoms are smaller than Ag atoms, thus they interfere more with the displacement of atoms in the alloy.

• Cu atoms are less polarizable than are Au or Ag atoms, thus Cu has weaker interparticle forces.

Which of the following molecules contains only single bonds?

• CH_3COOH

• CH₃CH₂COOCH₃

• C₂H₆

• C₆H₆

• HCN

Which of the following molecules has an angular (bent) geometry that is commonly represented as a resonance hybrid of two or more electron-dot structures? (Topic 2.6)

• CO₂

• O₃

• CH₄

• BeF₂

• OF₂

Which of the following molecules contains exactly three sigma (σ) bonds and two pi (π) bonds? (Topic 2.7)

• C₂H₂

• CO₂

• HCN

• SO₃

• N₂

Of the following molecules, which has the largest dipole moment? (Topic 2.7)

• CO

• CO₂

• O₂

• HF

• F₂