A sample of 500 g of radioactive lead-210 decays to polonium- 210 according to the function \( \mathrm{A}(\mathrm{t})= \) yr. (d) Find the half-life. (a) The amount of radioactive lead remaining after 4 yr will be \( \square \mathrm{g} \). (Round to the nearest integer as needed.) (b) The amount of radioactive lead remaining after 6 yr will be \( \square \mathrm{g} \). (Round to the nearest integer as needed.) (c) The amount of radioactive lead remaining after 10 yr will be \( \square \mathrm{g} \). (Round to the nearest integer as needed.) (d) The half-life is about \( \square \mathrm{yr} \). (Round to two decimal places as needed.)

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.

Please select the molecule(s) that 1) its molecular shape is different from its electron group shape, and/or 2) the central bonds are not identical. NH3 BF3 PFF PF3

Based on your worksheet results, please match the following: [he molecular shape of NH 3 is [Choose ] [Choose ] [Choose ] [Che molecular shape of BF3 is [Choose] The molecular shape of PF3 is

w/w alcohol? How many milliliters of \( 95 \% \) w/w sulfuric acid having a specific gravity of 1.820 should be used in preparing 2 liters of \( 10 \% \) w/v acid?

Which of the following molecule(s) have lone pair electrons and/or non-identical central bonds? NH3 BF3 PF5 PF3