Acids, Alkalis and the pH Scale

A solution with a pH of 2 indicates a high concentration of hydrogen ions (H+), which signifies acidity. The pH scale ranges from 0 to 14, where values below 7 are considered acidic. A pH of 2 is significantly lower than 7, placing it in the strongly acidic category. This means the solution is much more acidic than a weakly acidic solution, which would typically have a pH closer to 6. Therefore, a pH of 2 clearly characterizes the solution as strongly acidic.

When sodium hydroxide (NaOH) reacts with hydrochloric acid (HCl), a neutralization reaction occurs, producing sodium chloride (NaCl) and water (H2O). In this process, the hydroxide ions (OH-) from sodium hydroxide combine with the hydrogen ions (H+) from hydrochloric acid to form water. The remaining sodium ions (Na+) and chloride ions (Cl-) combine to form sodium chloride, which is common table salt. This reaction exemplifies a typical acid-base reaction, where an acid reacts with a base to yield a salt and water.

When an acid reacts with a carbonate, a chemical reaction occurs that produces a salt, water, and carbon dioxide gas. The acid donates protons (H+) to the carbonate, which leads to the formation of the salt and releases carbon dioxide as a byproduct. This process is commonly observed in neutralization reactions, where the fizzing or bubbling from the released carbon dioxide is a characteristic sign. Therefore, the complete reaction yields salt, water, and carbon dioxide gas.

When carbon dioxide gas is bubbled through limewater, which is a solution of calcium hydroxide, a chemical reaction occurs. The carbon dioxide reacts with calcium hydroxide to form calcium carbonate, a white precipitate. This reaction is represented by the equation: Ca(OH)₂ + CO₂ → CaCO₃ + H₂O. The appearance of the white precipitate indicates the presence of carbon dioxide, making limewater a useful test for detecting this gas.

pH is a measure of the acidity or alkalinity of a solution, with a scale ranging from 0 to 14. A pH value of 7 is neutral, while values above 7 indicate increasing alkalinity. As the pH increases, the concentration of hydroxide ions (OH-) in the solution rises, making it more alkaline. Conversely, pH values below 7 indicate acidity. Therefore, a higher pH signifies a stronger alkaline solution, confirming that the statement is true.

Nitric acid, sulfuric acid, and hydrochloric acid are all strong acids commonly used in laboratory settings for various chemical reactions and analyses. They are characterized by their ability to donate protons (H+) in solution, making them essential for tasks like pH adjustment, synthesis, and as reagents in chemical reactions. Ammonium hydroxide, on the other hand, is a weak base and not classified as an acid, which is why it is not included in the correct answer.

When sulfuric acid reacts with copper carbonate, a double displacement reaction occurs. The sulfuric acid (H₂SO₄) reacts with the copper carbonate (CuCO₃) to produce copper sulfate (CuSO₄), water (H₂O), and carbon dioxide (CO₂). The carbon dioxide is released as a gas during the reaction, while copper sulfate remains in solution. This combination of products is characteristic of the reaction between an acid and a carbonate, confirming that copper sulfate, water, and carbon dioxide are indeed the correct products formed in this chemical reaction.