(Originais Teachy 2024) - Question Easy 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

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?

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?

Consider a salt that undergoes hydrolysis in water, producing a weak acid and a weak base. How to determine if the final solution will be acidic or basic? How to calculate the final concentration or pH of the resulting solution? Give an example of a salt and calculate the pH of the resulting solution.