(Originais Teachy 2023) - Question Medium of Sciences

In the Folha de São Paulo newspaper, on June 14, 2013, a report was published about the chemical weapons attack in Syria "[...] Sarin gas is odorless and invisible. In addition to inhalation, simple contact with the skin of this organophosphorus gas affects the nervous system and causes death by cardiopulmonary arrest. The lethal dose for an adult is half a milligram. [...] Based on the information provided and chemical concepts, approximately how many molecules are there in an approximate lethal dose of sarin gas? Given: Consider the molar mass of sarin gas to be 140 g/mol. Avogadro's constant: 6.10^{23} entities.

The evolution of the Solar System is a complex process that involves the formation of stars, planets, and other celestial bodies from a large cloud of gas and dust. Studying this evolution not only expands our knowledge of the cosmos but also allows us to understand fundamental aspects of physics and chemistry. On the other hand, ancient cultures developed mythologies and interpretations about the origin and evolution of celestial bodies, often based on astronomical observations and their own traditions. Considering the historical and scientific context, describe the evolution of the Solar System from its beginning in a molecular cloud to the formation and stabilization of planets. Explain how the observations and interpretations of ancient cultures can be related to this evolutionary process, even though they did not have the scientific knowledge we have today.

Natural phenomena can be considered as extremely important events for our planet, as they influence the climate and the life of the species that exist on it. For example, rains are necessary to keep the rivers and lakes full and thus ensure drinking water for all living beings that depend on it to survive. Which of the following is an example of a natural phenomenon that contributes to the balance of the Earth?

In the solutions used in laboratories, the concentrations of ions $$\mathrm{H}_{3} \mathrm{O}^{+}$$ are usually small and a simple way to express the hydrogenionic concentration of a solution is through pH. Solutions of weak acids and bases present, in solution, an equilibrium between the various particles and, in this case, we have the equilibrium constant, that is, the ionization constant. A solution of $$1.10^{-3} \mathrm{mol}^{-1}$$ of bromoacetic acid $$\left(\mathrm{BrCH}_{2} \mathrm{CO}_{2} \mathrm{H}\right)$$ has an ionization constant equal to $$6.3.10^{-5} \mathrm{e}$$ and a solution of $$1.10^{-3} \mathrm{mol}^{-1}$$ of 4-chlorobenzoic acid $$\left(\mathrm{ClC}_{6} \mathrm{H}_{4} \mathrm{CO}_{2} \mathrm{H}\right)$$ has an ionization constant of $$1.0.10^{-4}$$. Given the following statements, I. 4-chlorobenzoic acid has a higher $$\mathrm{pH}$$ than bromoacetic acid. II. Bromoacetic acid is weaker than 4-chlorobenzoic acid. III. Since the concentrations are equal, both acids have the same $$\mathrm{pH}$$. IV. Bromoacetic acid has a higher $$\mathrm{pH}$$ than 4-chlorobenzoic acid. v. 4-chlorobenzoic acid is weaker than bromoacetic acid. It is verified that only ii and iv are correct.