Select the single best answer. Select the statement that correctly describes the hybridization of phosphorus in \( \mathrm{PF}_{5} \). Phosphorus is \( s p^{2} \) hybridized. Phosphorus is \( s p^{3} \) hybridized. Phosphorus is \( s p^{3} d \) hybridized. Phosphorus is \( s p^{3} d^{2} \) hybridized.

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.

Un laboratorio requiere de \( 2000 \mathrm{~cm}^{3} \) de una solución anticongelante que consiste en \( 30 \% \) mol de metanol en agua ¿Qué volúmenes de metanol puro y de agua pura a \( 25^{\circ} \mathrm{C} \) se deben mezclar para formar los \( 2000 \mathrm{~cm}^{3} \) de anticongelante tambièn a \( 25^{\circ} \mathrm{C} \) ? Asuma qué es una solución ideal. Los volúmenes molares parciales para el metanol y el agua en una solución de \( 30 \% \) mol de metanol y sus volumenes molares de especie pura ambos a \( 25^{\circ} \mathrm{C} \) son los siguientes: Metanol (1) \( \quad \overline{V_{1}}=38.632 \mathrm{~cm}^{3} / \mathrm{mol} \quad V_{1}=40.727 \mathrm{~cm}^{3} / \mathrm{mol} \) Calcule además el error que se produce al asumir que la solucion es ideal.

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

Nếu một mẫu chất phóng xạ bắt đầu với 100g và giảm đi 12.5% mỗi giờ, tính khối lượng còn lại sau 4 giờ.

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]