Using Dobereiner's law of triads, the missing number is \( \frac{\mathrm{Li}}{7}, \frac{\mathrm{Na}}{20}, \frac{\mathrm{~K}}{20} \).

Select the single best answer. Which of the following describes the bonding in the hydrogen cyanide molecule, HCN? As N is \( s p \)-hybridized. C uses \( s p \) hybridized orbitals in bonding. C uses \( s p^{2} \) hybridized orbitals in bonding. C uses \( s p^{3} \) hybridized orbitals in bonding. C uses \( s p^{3} d \) hybridized orbitals in bonding.

Question B 2 The following redox reaction is used in acidic solution in the Breathalyzer test to determine the level of alcohol in th blood of drunk drivers: \[ \mathrm{H}^{+}(\mathrm{aq})+\mathrm{Cr}_{2} \mathrm{O}_{7}^{2-}(\mathrm{aq})+\mathrm{C}_{2} \mathrm{H}_{5} \rightarrow \mathrm{Cr}^{3+}(\mathrm{aq})+\mathrm{C}_{2} \mathrm{H}_{4} \mathrm{O}(\mathrm{aq})+\mathrm{H}_{2} \mathrm{O} \] a) Identify the elements undergoing changes in oxidation state and indicate the initial and final oxidation numbers for theseelements.

\( CH _ { 3 } COOH + H _ { 2 } O \rightarrow \)

c. 5-etil-5metil-1,3-ciclohexadieno

Question B2 The following redox reaction is used in acidic solution in the Breathalyzer test to determine the level of alcohol in tl] blood of drunk drivers: \[ \mathrm{H}^{+}(\mathrm{aq})+\mathrm{Cr}_{2} \mathrm{O}_{7}^{2-}(\mathrm{aq})+\mathrm{C}_{2} \mathrm{H}_{5} \rightarrow \mathrm{Cr}^{3+}(\mathrm{aq})+\mathrm{C}_{2} \mathrm{H}_{4} \mathrm{O}(\mathrm{aq})+\mathrm{H}_{2} \mathrm{O} \] a) Identify the elements undergoing changes in oxidation state and indicate the initial and final oxidation numbers for these elements. [5] b) Write and balance the oxidation half-reaction.[6] c) Write and balance the reduction half reaction.[6] d) Combine the half-reactions to produce a balanced redox reaction. [3]