(UESPI 2010) - Question Easy of Chemistry

Among the amphoteric oxides, what is the oxidation number of chromium, respectively, in these compounds?

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.

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?

Organic salts are compounds derived from the reaction of an inorganic base with a carboxylic acid. These compounds have distinct characteristics from inorganic salts, such as solubility in organic solvents and soap and detergent properties. A classic example of an organic salt is sodium acetate, which can be obtained by the reaction of acetic acid with sodium hydroxide. Given the formula of acetic acid (CH3COOH), identify the inorganic base that, when reacting with acetic acid, forms sodium acetate. This reaction is an example of: