2. Una solución acuosa de amoníaco \( \mathrm{NH}_{3} 0,25 \mathrm{M} \) tiene un Kb de \( 1,8 \times 10^{-5} \), presenta disuelta una sal de cloruro de amonio \( \mathrm{NH}_{4} \mathrm{Cl} \) en una concentración de \( 0,45 \mathrm{M} \). a. Calcule el pH teniendo en cuenta ambas sustancias disueltas. b. Calcule el pH suponiendo que solo está presente el amoníaco. c. Escriba una conclusión teniendo en cuenta los resultados de los incisos a y b.

There are different types of food coloring available in most grocery stores- one that is water-based, and one that is oil-based. The oil-based food coloring works best in chocolates, in fry-oil to color fried foods, and in food with high butter contents. Based off of this information and knowing that substances of like polarity mix readily with one another, which food coloring is more polar (water-based or oil-based)? Which food coloring is less polar (or even nonpolar)? Water-based [Choose ]

Please select the molecule(s) with resonance structures from the following. CCl 4 CHCl 3 SO 3 H 2 O None

Please select polar molecule(s) from the following. \( \square \mathrm{CCl} 4 \) \( \square \mathrm{CHCl} 3 \) \( \square \mathrm{CO} 3 \) CO 2

Based on your worksheet results, please match the following: The electron group geometry of NH 3 is The electron group geometry of BF 3 is [Choose ] The electron group geometry of \( \mathrm{PF5} \) is [Choose ] [Choose ] electron group geometry of SF4 is geometry of PF 3 is [Choose ]

L'uraninite, ou pechblende, est un minéral de formule chimique \( \mathrm{UO}_{2} \). Les gisements d'uraninite sont datés uniquement entre 3,5 et 2,2 milliards d'années. Its sont utilisés notamment pour extraire l'uranium uti- lisé dans l'industrie nucléaire civile et militaire. Ces gisements se forment dans des milieux réducteurs, c'est-à-dire en absence de dioxygène. Question Expliquer en quoi l'uraninite est un indice de l'évolution de la teneur en dioxygène terrestre.