(Originais Teachy 2024) - Question Hard of Chemistry

During a Chemistry class, a 1st-year high school student realized that the concept of mole, essential for understanding chemical reactions, could be applied in a daily life context. He decided to analyze the bread-making process to understand the importance of measuring the amount of reactants, such as yeast, to ensure the quality of the final product. Considering that 1 mole of any substance contains approximately 6.02 x 10^23 elementary entities, and knowing that biological yeast is a mixture of compressed yeast cells and starch, the student proposed the following calculation: 'If a baker uses 25 g of biological yeast to make 3 loaves of bread, and each loaf requires exactly 8 g of yeast for the dough to rise properly, what is the amount of matter, in moles, of biological yeast that the baker uses in each loaf?' Based on this information, answer: 1) What is the relationship between the mass of yeast used per loaf and the molar mass of yeast? 2) What is the practical importance, in terms of bread quality, of measuring the correct amount of yeast matter used in each loaf?

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 search for alternative and more sustainable energy sources has led to the development of fuels composed of mixtures with ideal combustion characteristics. One of the challenges in this process is the improvement of the energy efficiency of internal combustion engines, which depends, in part, on the uniformity of the fuel mixture. Considering an internal combustion engine, where the efficiency of the fuel burning process is directly related to the homogeneity of the air-fuel mixture, a chemical engineer decides to investigate the behavior of different mixtures under pressure and temperature conditions similar to those found in the combustion chamber. For his analysis, he selects two mixtures: the first one is atmospheric air, mainly composed of nitrogen (78%), oxygen (21%), and other gases in lower concentrations, known to be a homogeneous mixture; the second one is a mixture of ethanol and water, in which ethanol and water form two distinct phases due to their differences in polarity and intermolecular interactions, considered a heterogeneous mixture. Based on the concepts of homogeneous and heterogeneous mixtures, which of the two mixtures investigated is more suitable to be used as fuel in an internal combustion engine, considering the goal of maximizing the energy efficiency of the burning process?