(Originais Teachy 2023) - Question Medium of Chemistry

Consider that a group of students conducted an experiment in the Chemistry laboratory by mixing 10 grams of salt (sodium chloride) in a cup containing 200 mL of water. After the mixture reached homogeneity, we call this mixture a solution. Calculate the concentration in g/L of this solution and identify which of the alternatives below best describes the relationship between solute, solvent, and concentration in the solution?

Nitro compounds are organic compounds that have one or more nitro groups (NO2) directly attached to a carbon atom of an alkyl or aryl group. They are commonly used as explosives due to their ability to rapidly decompose and release gases. Considering the IUPAC nomenclature rules for nitro compounds, answer: a) What is the correct nomenclature for the compound CH3CH2NO2? b) Write the molecular structure of 2,4-dinitrotoluene and identify the functional groups present in the molecule. c) According to the IUPAC rules, what is the name of the organic compound formed by substituting the three hydrogens of methane with three nitro groups?

The German chemist Friedrich August Kekulé was very important for the development of organic chemistry by presenting his postulates on the structure of organic compounds in the 19th century. One of his most important postulates is the tetravalence of carbon. Considering the concept of tetravalence and covalent bonds in organic molecules, answer the following questions: a) Explain why carbon is tetravalent, and briefly describe the relationship of this concept with covalent bonds. b) Give examples of three organic compounds that have tetravalent carbon and their respective structural formulas. c) Describe how the postulate of carbon tetravalence was fundamental for understanding the structures of organic compounds in Kekulé's time and, consequently, how it influenced organic chemistry in general.