(Originais Teachy 2023) - Question Medium of Chemistry

A white solid presents the following properties: I. It is soluble in water. II. Its aqueous solution conducts electric current. III. When pure, the solid does not conduct electric current. IV. When melted, the resulting pure liquid does not conduct electric current. Considering this information, the solid in question can be

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?

It is known that acetone is a type of ketone widely used as a solvent in the industry, mainly for the production of plastics, paints, and varnishes. Furthermore, studies show that its use can pose risks to human health and the environment. Considering the context, answer: a) Describe the general structure of a ketone and what sets it apart from other functional groups. b) Identify and explain some of the risks associated with exposure to acetone for health and the environment. c) Propose individual and collective measures that can be adopted to reduce the negative impacts caused by the responsible use and disposal of acetone.

A chemical laboratory received a sample of a new metallic oxide, and the scientists must determine the chemical formula of the compound based on its properties. The sample reacts with water, forming an acid that, when analyzed, reveals the presence of hydrogen and a metal that behaves as a divalent metal in its reactions. Additionally, the sample reacts with diluted hydrochloric acid, forming a metal chloride and water. If the mass of the metal present in the sample is 27g, determine the chemical formula of the metallic oxide and explain the reasoning used, including the nomenclature of the compounds found.